If the only reason we practice piano is to "get better," then we're often setting ourselves up for failure. Instead, let's take a healthier look at the practice/enjoyment/improvement cycle:
If you love the act of making music so much that you completely enjoy playing piano at your current level, that's a wonderful attitude to have! It's the same as I have, and this is what helps us get better as pianists, too. We'll stay actively involved at the piano and we will improve almost as a by-product of our interest and enthusiasm.
Don't bring yourself down by self-criticism. Enjoy every single moment you're at the piano, whether you're performing the simplest song in the world or practicing a challenging new technique. That's what's going to get you practicing more, by practicing more, you'll automatically get better.
This is an important concept: The more we enjoy ourselves at the piano, the more we'll want to play. And the more we play, the more we'll improve. (Our musical improvement can be seen as almost a "by-product" of our enjoyment, not the other way around!)