The only real measure
Can you solve the problem on a blank page, from memory, with nothing in front of you? That is the only question, and every other feeling you have about your preparation is noise.
'I understand it' is not the standard. Understanding a solution is a low bar that reading clears easily and exams do not accept.
Practise choosing, not just executing
Most maths revision is done in blocks: twenty integration-by-parts problems in a row. After the first one, you already know the method — the exercise told you. So you practise executing a technique you were handed, and never practise the thing the exam actually tests, which is *deciding which technique*.
Interleave: mix problem types so every question forces a decision before it forces a calculation. Your practice accuracy will drop and your exam performance will rise. That trade is the whole of learning science in one sentence.
The routine
- Attempt before you look. Always. Even a failed attempt makes the solution far more instructive — see self-explanation.
- When stuck, look at one line only. Then close it and continue alone. Reading the whole solution is how you learn nothing.
- Redo problems you got wrong, days later. Immediately afterwards you're pattern-matching on the solution you just read, which measures nothing.
- Automate the basics past boredom. If standard derivatives take conscious effort, they're eating the working memory you need for the actual problem — and you'll conclude you're bad at the problem.