Learning to accept things you cannot change is one of the hardest things I've had to learn growing up.
Constant black and white thinking and cognitive distortions [0] all will increase your anxiety. Realize these emotions' utility and purpose. These feelings are meant to provoke action or change by you to improve your life. Constant negativity about things you have no control over cannot and will not ever help you.
It's good to practice questioning yourself when you're being crabby. Nothing in the world is 100% negative. The world is a lot more gray then black or white.
Try to challenge your assumptions about the world a bit more. Accept that maybe you don't know everything, and you almost never have the whole story, and use that to feel better.
For example, you may think that you're being ripped off constantly. You can challenge that with "at least it's keeping people working, and providing for their families". Maybe what you consider being "ripped off" isn't actually you being ripped off, maybe it's expensive to make these books. Don't think of it as 100% of the cost is a rip off. Maybe be like, well at least the books are worth 75% of what I paid for them.
In essence, if you cannot fix an issue yourself, you have to learn how to not care so much by either lessening the negativity of an event by challenging your emotions, either by turning negatives into a positive, or letting it just not affect you because it's not worth it.
Between learning to accept things I cannot change and learning to change things I cannot accept, I find them both equally difficult, so I have opted to pursue the latter as it's at least mildly more interesting.
It's not really a one-or-the-other kinda deal. It's not a fork in the road. Acceptance of things you cannot change isn't an opt-out whilst it is possible to opt out of trying to change things that you could change if you tried. But accepting things out of your control IS a change in itself.
Make an effort to discard the anger, bitterness, and confusion that results from "things you cannot change" and you'll probably find it easier to focus on the things you can change.
Whether it's interesting or not doesn't (shouldn't) really factor into improving one's long-term mental health.
Constant black and white thinking and cognitive distortions [0] all will increase your anxiety. Realize these emotions' utility and purpose. These feelings are meant to provoke action or change by you to improve your life. Constant negativity about things you have no control over cannot and will not ever help you.
It's good to practice questioning yourself when you're being crabby. Nothing in the world is 100% negative. The world is a lot more gray then black or white.
Try to challenge your assumptions about the world a bit more. Accept that maybe you don't know everything, and you almost never have the whole story, and use that to feel better.
For example, you may think that you're being ripped off constantly. You can challenge that with "at least it's keeping people working, and providing for their families". Maybe what you consider being "ripped off" isn't actually you being ripped off, maybe it's expensive to make these books. Don't think of it as 100% of the cost is a rip off. Maybe be like, well at least the books are worth 75% of what I paid for them.
In essence, if you cannot fix an issue yourself, you have to learn how to not care so much by either lessening the negativity of an event by challenging your emotions, either by turning negatives into a positive, or letting it just not affect you because it's not worth it.
[0]: https://en.wikipedia.org/wiki/Cognitive_distortion