Did you forget a lot from your physics education?

I‘m currently doing my masters in physics and I‘m kind of struggling. I know I can do it, it‘s just hard. I seem to have forgotten a lot from my Bachelors, like I once used to know how to solve, or at least approach, the different kinds of differential equations. Now I have to look that up almost all the time. Another example would be Lagrangian and Hamiltonian mechanics, altough I didn‘t need these formalisms in my master studies yet.

Does anyone have similar experiences or do I just have physics-Altzheimers?