Feel bad? It feels so much worse than that. I hit a stall at about the two hour (maybe two and a half, depending) point when I draw. And after that, no matter how much a force myself to draw lightly and mindfully, nothing comes out looking the way I want it to. Every line just seems forced and misplaced and even going back to fundamentals doesn't feel right. I have to physically get up and walk away from my sketchbook / computer and do something else because after those two hours I just can't draw. No matter how many times I flip the image, everything I do seems to reverse my progress, in my eyes.
It's horribly frustrating and I feel so fucking inadequate. Like my brain and my hand are no longer in homeostasis. It's.. hard to explain - it's like art block hits me every time I draw past two hours without fail but instead of not knowing what to draw, I can't even finish what I started! It's also a big reason you don't see me color much because I have an even lower tolerance for that.
But, then I give myself some time to chill, and after like an hour and a cup of tea I'm usually recharged and ready to draw again. So remember, no matter how talented you are, there's nothing wrong with giving yourself and your piece some space. It'll do more than just give you a different perspective once you get back to it, it resets your artistic control panel, if that makes any sense, haha.
Be patient, don't compare yourself to others, and don't be so hard on yourself. It's a lesson all artists can stand to be reminded of.