Have you secretly asked yourself, I got a great well paying job, but I'm still unhappy with it? Maybe its too stressful or too boring. Maybe you find yourself doing endless repetitive tasks or you have no tasks at all. You keep telling yourself you should be happy since others have way worst jobs than yours and would die to be in your place. You suppress that desire to quit as you get paid better than a major of people in the world.
Some people say you're a hedonic treadmill. Initially, you achieved a great high when you first got your job. But now you've sink back to your base line as the novelty of the new job is gone and you're in a routine schedule now. I agree some folks may be on a hedonic treadmill but I believe others are unhappy with their job because their job doesn't allow for them to have a creative outlet.
A lot of people who are in software engineer have jobs building and maintaining large and complex software at companies. They assigned a small component of the software and are tasked to build and maintain it. They never see the end results; they never see the impact it makes. Some might think their jobs might be a "bullshit" job as whatever they're working on has no difference whether its done or not.
People yearn to build things have other people use and enjoy that thing. People yearn for a creative outlet. Next time at work, take projects or assignments that make a bigger impact on end users or the company if you can. If you can't find, try building stuff outside of work. Take up a side project. It doesn't have to be able to making more money. if you fancy writing; start a blog. if you like tinker with software, build something and open source it. if you like video, create compelling videos and upload to YouTube. Build something; anything and share it with the world. Seeing people thoroughly enjoying it will make you 10x happier than you ever be.