When you give your own view or reaction, 觉得 is the everyday choice: 我觉得这个安排太赶了 means “I think this schedule is too tight.” It can report a feeling as well as an opinion, so it leaves room for other people to see things differently.
以为 starts from what someone had taken to be true. It often appears just before a correction: 我以为会议十点半开始，结果是十点. That little 结果 is a useful clue—the speaker is looking back at an assumption that did not hold. If you are simply offering your view now, choose 觉得; if the point is that you had the wrong picture earlier, choose 以为.
