My parents actually had a good approach to things like this. It wasn't my ability or result that was praised or ctiticised, but the effort I put into in. So, if I was writing or drawing something, and had put a lot of effort into it, then I was praised for my effort. Good effort often brings good results, and that was also praised. If the effort didn't yield good results, that didn't matter, I was still praised for making the effort. However, if no effort was put into something (usually yielding mediocre results), then I was not praised but criticised and told to try harder nest time. I think that this was fair, and something that I try to apply to my students.