Staying motivated at work

I keep struggling to stay motivated at work. Like right now I am doing a tedious repetitive task that’s taking a few days to complete and I really struggle to stay focused on it and interested in it. Then my pattern at the end of the day is to think that I didn’t do enough. I also worry about making mistakes and not doing things right and about maybe this job isn’t a good fit for me, which I KNOW is a thought because it keeps following me wherever I go lol. But I can’t seem to shift it to something else yet.

I can sometimes coach myself to feeling motivated and inspired about how I can show up at my job, like bringing the coaching stuff I’ve learned to our team and being a leader of sorts and figuring out how to bring a common vision to our team to produce better quality. I am a quality assurance specialist and was hired to change our processes, which means changing how people work and I want to stop feeling stressed and anxious and guilty/ashamed all the time, especially in the evenings when I’m not working.

How can I unravel this more?