My Mac feel better with 4GB memory than 8GB

About two months ago I have been decided to upgrade my MacBook Pro memory from 4GB to 8GB. This is the second MacBook Pro ever I have or the seventh notebook for me. In the first day of using MacBook with new memory installed inside, I think my MacBook will work better than before, but I don't feel it till now. The unfortunately, contrary condition has been appeared :(


I have been replaced new memory with the old (original) memory now.