Now, I should not care. I am not their boss and their work does not
directly impact mine, so objectively there is no reason for me to be
annoyed by this, but the fact that I feel that I make a bigger effort
than them in our small company to achieve success does bothers me.
Clearly this is about your feelings, and feelings are personal.
What helped me ...
Stop presuming that you are a virtuous person
Obviously, your entire position here rests on the presumption that you are a good guy, honorable and hard working. From that high horse, you judge everyone else.
And you presume that judgment is also virtuous.
You don't even think about this; you just take it for granted.
Another person ...
I'll play a bit of the devil's advocate here.
How to properly let it go how coworkers around me are performing, when they do not affect my job and I do not have a manager position?
You're wrong here, three times in a single statement. Stop lying to yourself. They do. They already did affect your job. You think about them, you care about them (even if in ...
Having been in this situation many times, the answer is as you implied: it's not your job to care, so, don't. It is your manager's job to assess performance of your colleagues, not yours. Presumably, your manager has some way of measuring performance in a consistent manner (tickets, call times, sales, something relevant to the job you do), and also less ...
It can be interesting to look at this from the company's point of view...
If you had 2 cars and your wife's got poorer mileage/needed more repairs would you throw it away? Maybe? Maybe not right away? Maybe not at all? Sometimes you keep the sub-optimal one because it's better than the alternatives (Not having one or buying a new one).
In some cases I ...
It is a natural reaction. Give one small child 2 sweets and another 5 sweets in front of each other and the one with less will complain of unfairness in spite of the fact that there is no reason to guarantee they would get more sweets (please don't actually do this).
Now you are not a child but it is a sense of fairness that never leaves us, we just tend ...
Warning: I am going to make an assumption that you are either a developer/sysadmin, but much of what I will say apply for many positions.
Question: do you want to stay on that company for the next year? 5 years?
Hint: it is not the only place you can get a job.
Like @vaxquis said, document everything, specially emails praising your work and reports of ...
From comment: I want to stop getting bothered by it.
What you are doing is
comparing yourself to a standard with "I should not care", "objectively there is no reason why"
finding that you do care, so you are not meeting your standard
feel bad about that as well
This is like having failing code which throws a divide by zero error, putting a unit ...