hmm, I think most of our thinking happens through habits and breaking through them can be hard.
I think often the very root of negative thinking is a lack of self esteem and therefore general dissatisfaction with life, which leads to a negative world view.
I don't know you but maybe meditating could help, or doing a hard reset of your brain using psychedelics.
I chose the latter which is the fast and easy way but it still took me about 2 years from realising my problems to solving them.
Life really is just how you think of it, so working towards a more positive mindset is time well invested.