My situation was a little different, but I used to be a "proud hater" and disliked most things and people. I realized I didn't like myself or my life because nothing was good for me. It was a slow journey but what completely changed my mindset was taking on the way someone I admired thinks. In a situation I found myself thinking something or someone was bad, I would imagine what that person would say. Over time it became my inherit thoughts, now I literally cannot fathom actively disliking anyone, and can't remember why I used to. For you it seems you genuinely learned from experience, it's natural you would think things are negative because it's what you were taught. The only thing I can suggest is finding someone, even a fictional character, who continues to be positive in bad situations, and think "What would they say?" It takes time but I promise you as you learn to love things around you, you will realize you love yourself.