The Sun is most adversely affected and thus has least strength, based on what is called essential and accidental dignity/detriment [which then would point to success, but not without looking at the strength of other planets] in AQ, the sign of Sun's detriment. Sun is also weak in Pisces, but not as much as in AQ. Then it is marginally stronger in Cap. It is then somewhat stronger in Sag, especially at certain upon its degree.
So Sun in Sag may point to success, followed by being in Cap, then Pisces, then Aquarius. But that all may be undone by the Sun's house and its relation to all the other planets.
One really can't draw extensive or meaningful conclusions by looking at a single planet in a sign.