This is perhaps the aspect which leads the charts in Indian astrology when it comes to misconceptions in different sections of astrology. Most of the people interested in astrology as well as many astrologers themselves are deceived in predicting the formation of a good or bad yoga in a horoscope. Many people and astrologers think that the presence of a particular planet in a house or the combination of two or more planets by placement or aspect is the only thing required to predict the presence of a Yoga in a horoscope. For example, a Kuja Dosha is considered to be present in a horoscope by most of the people as well as many astrologers, just by the placement of Mars in the houses 1,2,4,7,8 and 12 of a horoscope counted from the Ascendant and it is considered that the people having such placements of Mars in their horoscopes are all having a Kuja Dosha in their horoscopes and are going to suffer with delayed and disturbed marriage which may even lead to a divorce or death of the spouse.
In the same way many astrologers think that if all the seven planets namely The Sun, The Moon, Jupiter, Venue, Mars, Mercury and Saturn are placed between Rahu-Ketu Axis in a horoscope, a Sarpa Dosha is formed in that horoscope which is capable of doing serious damage to the person having Sarpa Dosha in his horoscope in all spheres of his life which may include career, marriage, producing children and many other aspects of life. The above mentioned defects namely Kuja Dosha and Sarpa Dosha are indeed capable of doing serious damages to the person suffering from them. But the important thing to consider is that the placement of Mars in the above mentioned houses in a horoscope is just the primary condition for the formation of Kuja Dosha in a horoscope and it is not the final confirmation. In the same way, the placement of all the seven planets between Rahu-Ketu axis is the primary condition for the formation of Sarpa Dosha in a horoscope and not the final confirmation. Once the primary condition for the formation of a defect is present, it is further checked for the confirmations. And if the confirmations are all present in a horoscope for the formation of a defect, only then the defect is formed and then its strength, field of impact and timing of impact is calculated to predict the results.
Moving on to some of the Yogas which are considered very good in Vedic astrology, the same thing is true for predicting a good yoga also. For example one of the most famous and auspicious yogas in Vedic astrology is GajaKesari Yoga which is considered to be formed if Jupiter is placed in 1, 4, 7 or 10th house counted from the house where Moon is placed in a horoscope. To simplify, if Moon is placed in Aries in a horoscope, the native is said to be having a Gajakesari Yoga in his horoscope if Jupiter is present in any one of the signs namely Aries, Cancer, Libra and Capricorn. In the same way a BudhAditya Yoga is said to be formed in a horoscope if the Sun and Mercury are present together in any house of a horoscope. The meaning of Budh is Mercury and that of Aditya is the Sun, so it is a Yoga formed by the Sun and Mercury in simple language. The native having this yoga present in his horoscope is considered to be blessed with great intelligence and benefit particularly from the house of government.
However it is important to note that in both of the above mentioned Yogas, the conditions described above are just the primary conditions for the formation of these Yogas and they do not mean the confirmation of these Yogas in a horoscope. And seen scientifically , the primary condition for the formation of GajaKesari Yoga in a horoscope is met in every third horoscope on an average, as it is formed due to presence of Jupiter in one of the 4 houses among the 12 houses of a horoscope which becomes one third. Gajakesari Yoga is a very powerful Yoga and it is capable of blessing the native with great wealth and fame which is obviously not seen in case of every third individual. In the same way, the Sun and Mercury are placed in the same sign in almost every second horoscope as the Sun and Mercury move usually very close to each other. This would mean that every second person in this world is very intelligent and getting good benefits from the house of government, which is again not seen in actual practice.
And it would again lead us to the fact that a particular combination of planets in a horoscope for the formation of a Yoga is only the primary condition and not the confirmation for predicting the Yoga in that horoscope. Most of the people told to be having GajaKesari Yoga in their horoscopes are not rich at all and on the other hand many of them are suffering from poverty or belong to the middle class and are far away from fame. In the same way, most of the people told to be having a BudhAditya Yoga in their horoscope are far away from being very intelligent and are not getting any major benefits from the house of government. And same is the case with all other good and bad yogas. This is all because of the fact that the functional nature of the planets involved in a Yoga is the foremost thing to be seen for the confirmation of a Yoga. If any of the planets involved in the formation of a good yoga is working negatively in that horoscope, the positive yoga is not formed at all and on the other hand the yoga becomes negative in which case the significances ruled by the positive planet would suffer due to the bad effect of the negative planet.
For example, suppose a combination of the Sun and Mercury is present in a sign in a horoscope satisfying the primary condition for the formation of BudhAditya Yoga. The first test done for the confirmation is to check whether both the Sun and Mercury are working positively in that horoscope or one of them is negative. If one of them is working negatively in the horoscope, the positive yoga is not formed and instead a negative yoga is formed. For instance if Mercury is negative and the Sun is positive in a horoscope, then the result of the combination of the Sun and Mercury in a sign is the formation of a negative Yoga in which the significances ruled by the Sun are affected negatively by the negative effects of Mercury. In the same way the significances ruled by a positive Mercury are affected negatively if the Sun is working negatively in a horoscope and the Sun-Mercury combination is found in that horoscope. And in the worst case, if both of them are working negative in a horoscope, the results of this combination would be disastrous and quite the opposite to the positive effects mentioned for BudhAditya Yoga. A native having a combination of the Sun and Mercury in his horoscope where both of them are working negatively, is likely to be having no intelligence at all or little intelligence and is likely to suffer from defame or people mocking him in general.
Now we can see that the combinations look all the same in all the cases, but the functional nature of the planets involved in those combinations can completely change or reverse the resultant effects of the Yogas formed. Therefore a Yoga should not be predicted by only looking at a certain combination of planets which is the primary condition for the formation of that yoga, as the results may be totally opposite to the predicted ones if both the planets involved in the combination are negative. And even if a good yoga is confirmed in a horoscope, it is checked for strength, the field of impact and timing of impact before predicting the results for that yoga. Same is the case with the confirmation of negative yogas. For example, a positive Mars placed in the above mentioned houses of a horoscope does not form Kuja Dosha and instead a Manglik Yoga is formed which gives very positive results and the native having this yoga in his horoscope is blessed with a very good married life with all around happiness.