It's just about restraint really... I notice it myself when I am just laying down a few loops or noodling over a backing track (especially if I record it and listen back after) - very easy to play without a lot of purpose/melody and a lot of "flash" but no substance and get carried away. Sometimes I try things like forcing myself to only use, let's say, a maximum of 3 notes per bar or something like that - not enough to bust out any overused licks or waffle-y bloated stuff and actually can sound quite bad if you don't try hard to make an impact with phrasing, melody, choosing those 3 notes very wisely and thinking about how they fit into what's going on in the backing. A bit similar to the whole "solo on 1 string" idea - restrict yourself to force yourself into exercising your mind/ear in a way that you normally wouldn't