When to "level up"?

Going back to self study math, when do you typically decide to move on to the next subject?

In college it was easy, whenever the semester is done. But now that im going back there really isnt an answer, at what level of Calculus should I be ok moving on to discrete mathematics or anything else.

Could always get better in any given subject as well so do you find its best to stick and master one or bounce around?