You just can't do that. The idea is that you know one strong password, but that's it. Everything else is randomly generated using KeePass and you don't ever have to know it. Obviously you might want to use a password you know for things you access when away from a computer that has access to KeePass, but all those sites you access once a week or month should be random.
If you're really worried about forgetting it, they you could write it down somewhere. If you do this though, at least split it into two parts and store them in separate places.