when does it kick in?

I go into lab everyday hoping that I'd get some kind of epiphany, some kind of indication that I've understood. It sort of reminds me of that one time I ran a 5-mile fun run and my brother-in-law kept telling me that after a while it will "kick in" like it would stop feeling like my lungs are about to explode and then suddenly the rest of the race will be a breeze.