How, then, to study mathematics?

If there is not enough intelligence, how to learn math? In mathematics can only understand the algorithm of doing something, when it to explain why so - and-so didn't understand. And vitamins drinking and all - does not help. And a bad memory - I keep forgetting. Elementary knowledge of mathematics was still at school within the algorithms. I tried to study high school physics - the mathematical knowledge for it was useless, because he moved hard and constantly forgot studied. I tried to study electronics, and also at the beginning I was blown away. It seems too difficult. Now decided to explore more seriously the math, but the explanations why it is also constantly hit a dead end. Especially geometry. And Soviet textbooks tried telling them clearly written, but not me. Want something on a serious level to learn, and intelligence is not enough. How to be?