Answer: Many caveats here – (a) Happiness differs from person to person – one may want many children, another may want more money, a third may want powerful position in job, another may want a powerful position in society, etc.
(b) Birth times may not have been accurately noted (see earlier answers where great people have said that don’t let horoscope “dictate” life)
(c) Some half-baked astrologers being bad apples and
(d) Human nature of astrologer (as described at earlier point of this q & a).
and many more have been discussed in previous posts...
(26 of 29 - Sathayam / Shatabisha)