overcoming background negative feelings: giving up, tired, defeated, depressed, hopelessness

Please provide sources from the original text or your own experiences and understandings of how to make progress in overcoming background negative feelings? For years I have been greatly harmed by harboring these feelings in the back of my mind which has not only created great suffering but altered the course of my life. Doing some mindfulness work made me realize that these feelings are there in my mind due to past experiences, and are harming me more than anything else in my life. How can I overcome, even slightly, this kind of mindset?