If your design career started as mine did, with a degree, you probably left university with a few misconceptions of how different designing in the real world is compared to the projects you worked on at uni.
One key thing I learned very quickly when entering the industry is that no matter how much of a perfectionist you are, you must be able to work within budgets and time constraints – on occasions, the need for speed is far greater, and there simply isn't room for perfectionism. Second to this, though, is the realization that this is okay. In an ideal world, we'd like every project we work on to be worthy of a top spot in our portfolio, but, in reality, the most important thing is that the result fulfills the client's needs on time and budget. There's always going to be a project that you're more proud of than others.
Having the time and budget to evolve a project until it is 'perfect' is a luxury not to be taken for granted. Always try to cut down time spent up either side of the creative process so that you have maximum time to let your ideas flourish.