I agree with a lot of what others have said.
I don't work on one stitching project at a time, and the ones that I work on are often quite different from each other. Some are small and simple, some have different stitches, more shading, etc.
I have been stitching for about a year and half now. Although stitching was my first (and I do greatly enjoy it), it was actually the thing that showed me that I have a passion for the fiber arts (I say passion and not obsession because my obsessions don't usually last this long). Sewing, knitting, spinning, stitching; I want to (and try to) do it all. I could talk about it for hours (and I have gone to retreats to do just that), and it's what I spend the time I'm not crafting thinking about. And while the fiber arts are all related in one way or another, the processes are also quite different and if I'm not in the mood to knit, I'm usually in the mood to stitch or sew (and vice versa).
There are other hobbies I like to do that I'm not as passionate about. For example, I love playing video games and can do so for a long while, but eventually I get burnt out on it. And I leave it and don't play again for a few weeks or months. And that's okay. Video games aren't going anywhere, and I know they'll be there when I want to get back to them. Same with jigsaw puzzles. Perhaps stitching is such a hobby for you. You may enjoy doing it for long stretches of time but then your brain may want to do something else for a while. Odds are, you'll get the hankering to do it again in the not so distant future if you enjoyed for this long. And that's perfectly okay! There's no point in making yourself do something you find boring. In the end, it's probably just going to make you actually not like stitching.
Basically, I'm trying to say that it's perfectly normal to feel bored.
P.S. - I highly recommend trying other fiber arts (like crochet). You may not like all of them, but odds are you'll like at least some of them if you enjoy stitching. Plus, it's just fun to try new things.
Careful though, if you're like me, you'll end up doing everything and then you'll just be running around in craft frenzy.
