Problem of proofs I've been away from math for a long time ,and while I was trying to relearn it using Courant and Fritz 's booknon calculus,I  loved the explanations but I couldn't solve any exercices(they're almost all proofs) and there isn't any solution manual,I guess I've been using too much of those plug and chug book .What do I do now?I don't solve them?read something else that teach that?what do you suggest I do?

Pretend you are writing an essay. That is what a proof is, basically; writing a formal essay. Have you also learned to read mathematics properly? Here is a link that has helped greatly. By reading actively, you will be more understanding of the proof at hand. It takes about 10 lines every 30 minutes for great mathematics comprehension, for example. http://web.stonehill.edu/compsci/history_math/math-read.htm
