I have a problem which I am unable to tackle to the best of my efforts. Whenever I learn a concept (maths, computers physics), if I am required to solve a question on it immediately, I do it without any problem. If I return to a similar problem later, say after two weeks, I can't think of anything on that problem. I know what concept will be applied but its all gone. I am not able to recall anything on that topic.
Why is this happening? I have tried everything - from trying to solve the same question twice or more times, regularly revising the concepts, etc. Regular revision does work. However, I think that the practice of redundancy can help only this far. What about situations in life where I can't revise concepts?