I am currently an adult student about to start a mathematics program at a university. I want to start preparing myself for analysis as soon as possible because I have a feeling it is going to be very difficult. So, I recently purchased Apostol's calculus book as well as Spivak's since I heard these are good books to get someone used to doing proofs. However, they seem to be a bit over my head. I am able to understand many of the concepts they are explaining, but when I get to the problems at the end of a unit, I don't have any idea where to start. Are there any books that would help get me to the level where I would be able to complete these two books?