How to fight nihilistic thoughts

Ill start off with the fact that i've been diagnosed with some of the most severe mental disorders out there, bpd, bipolar disorder and possibly schizophrenia

I am convinced that humanity is too dumb to live in an age of technology, I truly believe this is true. And it will take something absolutely cataclysmic to fix our problems. When I get into a dark mindset I start to give up on happiness, with this thought in my brain most of the time. I barley am keeping my head above water, sometimes through the day Ill get glimpses of distraction and happiness but most of the time I can not shake this mindset. All I want in life is to stand tall above the ocean of negativity, enjoy the small moments even if I know the world around me is destroying itself but I have yet to figure out a way to do that. I live in a constant state of dissociation because of this traumatic thought pattern. Love and affection is the only way I can seem to feel truly happy but when thats your only source it becomes toxic and when it doesnt work because you put all your effort into it, it is the absolute reality bending destruction of your very being most normal people cannot comprehend. I am on meds and in therapy but these fixes cannot change these thoughts engrained in my soul. Only provide a nice band aid to get me through the day.