Altered perception of your own music
Working on a composition for hours alters the way you perceive your own piece and is something to be very conscious about. Many composers tend to overwrite because having listened so many times to the same passage or piece will naturally leave you quite bored so the natural reaction would be to throw something in to make it interesting again for you. The problem is that with this strategy you’re simply overwhelming a listener who listens to it for the first time, who doesn’t know the thematic idea yet. So try to always imagine the focus of a first listener and try to get some distance from your own piece to find out whether it really needs something there to keep it interesting or if that is just you being longing for more because of fatigue.