Some days, one must just do what one can do.
Other days, of course, one must do much more than one is able to do: give it 110%. All right, that did not make any sense either.
I do stand by these words: I try to do all I can, as best I can, as soon as I can. It is just unfortunate that I want to be able to do more.
Small tip: Do your best and be proud of that achievement, however small. Learn how to do more and better work, and then live up to that.