We've all heard the phrase "Life is unfair." And you know what? I can agree! Life can completely be unfair. You can gain friends, but lose some as well.
Your life may be good, and you may have been taught 'you're the best.' But wait, newsflash! You're NOT. Get over it. There are people with shittier lives. You may be sitting on the beach, drinking a refreshing glass of water, and thinking life is great. Yet somewhere else in the world, someone could be getting raped, abused, or bullied.
Suicidal people and self-harmers know that life is difficult. That's why people do what they do. They self harm, attempt suicide, and look down on themselves because they've either been told it and believe it, or go through a lot and are tired of the pain.