Find happiness (and take joy from) in small accessible things. And do these happy things daily.
A sunset, sunrise, flowers in the park, blue sky, pooches with boop noses, a nice walk, the peace from sitting with a coffee in silence, tge idea is its small accessible things that you can access in multiples, you encounter and you can always find. (substitute for whatever makes you happy but small things, not expensive, not possessions), don't rely on others to make you happy, don't depend on Susan coming every Sunday etc. You need to be able to create and deliver your own happiness. A hobby or something to do as well, volunteer at a doggy day care, for example if you have the time if you enjoy interacting with the dogs.
And actually do take joy, it makes a difference to say "look at that, it's beautiful, isn't it nice, isn't it peaceful, it makes me happy" etc. It's not immediate but it works over time.
Stop saying negative things, "this is shit, ffs look at that, what the fk, can't be arsed with this, always the fkin same"
Your mood is impacted by how you act, and the people you interact with.
Small things.