I don't know if everyone feels this way, the same way that I do. But I doubt that there's some "ultimate level" of skill you can achieve where you think your art is perfect and there is no more improving to be done. Think of your favourite artist, and how much you admire their work - and I can tell you, they can see the flaws in their art just as clearly as you can see the flaws in your own. But in a way, it seems like a pointless endeavour, improving your skills, if you're not going to become any more proud of what you create, at least not for long. Perhaps you finish a piece and sit back and say "that looks awesome", but then after a day or two, the mistakes start jumping out at you, and you vow to do better next time. What's the reason in that?
But that's just it. Our ability to see the flaws in our own work is what makes us capable of improving, which is the very thing we so desire. If we always thought our work was perfect, why bother making it better? But our constant dissatisfaction (to some level) with our own pieces gives us our drive, and that's what makes us artists. We never stop drawing, becuase our thirst to better ourselves never ceases.
Perhaps the end result is something to be admired, and I do certainly appreciate my work after I create it, but what's more important, at least for me, is the journey. I'm not talking about creating one piece, but of ascending to the next level of artistic skill. And the next. And the next. It's a repetitive cycle, but one that I enjoy. Every day I can compare my current works to past ones, and say "woah, look how much I've improved!" Improvement, rather than success, is what motivates me, though I suppose improvement is a form of success onto itself. There is always, always more to be done in terms of aquiring artistic skill, but you can look back and see how far you've come. Perhaps that's what it means to be an artist. It is a journey, one that takes place over a lifetime. Achieving one milestone after another. You gain a deeper understanding of colour theory. You discover how to shade more realistically. You learn to draw a hand (and we all know how hard that is!) By all means look into the future, and dream about when you will be better, but keep glancing back into the past, and counting your achievements, and remembering your success stories. Art is fun, and exciting. There is always something new to be discovered.