I think that learning any launguage is built on,
1. how you learn it. If you learn a word wrong, you will pretty much never learn it right.
2. How much you use it. If you don't use English everyday, do you think you will remember it?
3. How you use it with others. This tyes in with the above. If you don't use it with others, how do you know how to use it in a conversation?
These are steps I used to learn English.