Breakthroughs happen and no doubt and they can happen anywhere. The most electrical is the one you have on stage. One night you just do something differently or try something new and your whole show forever. It can and does happen. You will know it when it strikes.....breakthrough!!! Oh yeah!
breakthroughs come in many forms.
Sometimes it's in the form of a punched up, juiced up punch line that suits you and your character better and so you begin writing like that more often.
Occasionally it's in a timing thing where you hesitated longer than usual on a punch oooor rushed through a bit more only to discover the energy is better served here or there.