Just that working with a formal definition will help you to develop correct mathematical intuition for the concept. They develop it by working with the formal definition. Because formal definitions are precise, they are one of the few places in mathematics where memorization can be useful. It may be worth collecting them in one place, to build up a calculus glossary. Learn the Theorems.
Theorems are another source of power for mathematics.
Because a theorem is something we know for sure . Working from precise definitions, mathematicians prove consequences of those definitions, and in doing so, they create theorems. There are few things in life as certain as a good theorem. Like definitions, theorems are stated precisely and should be rewritten and remembered in the same way. Read backwards and forwards.