How do you "let it go" at work?

My boss is always asigning me stupid tasks of proyects he doesn't know hoy they work.
Those tasks usually involve:
- a waste of time
- more work for me later
- breaking something that is currently working
- loosing the bonus in my salary for not achieving our goals

I try to explain it to him but he doesn't seem to listen or understand what i explain.

I try to remind myself that i dont own the company, that it is not my responsibility if something goes wrong and that, as soon as I get paid, i shouldn't care if i am wasting time.
But i can't seem to avoid feeling frustrated and burn out and get mad at the lack of organization and misleading. Its not my company, but i like doing a good job.

How do you manage these situations?
How do you "let it go" at work?
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