No matter what major you have (even leisure studies) you will not do everything right. You won't remember everything. It's not possible. The best thing you can do to help your studying and schoolwork is stop holding yourself to an impossible standard. Believe me, I know how difficult this is.

P.S.
If you are committed to a career in chemistry, don't doubt you can do it. There is no easy major if you don't want to do it. There is no impossible major if you are committed to a career in it.