Someone once asked...
Someone answered with kindness...
Because you have convinced yourself your best is not good enough. Somewhere down the line you've been conditioned to always need to do better. Whether it was from an external source or your own thoughts getting to you. That self-pity and distaste towards your own being has created a never-ending cycle of not being good enough. You think "If I do enough work, I'll finally have some worth" or "If I just exhuast myself right now, I'll be set", but when you use effort and success to try and dismantle self-hatred, you'll never be enough. At some point, saying "I'm a piece of shit" is gonna make you become a piece of shit. You are, scientifcally, what you think. There's always more to do, there's always more to reach, whether it's daily tasks or New Year resolutions that come every year. And because you constantly demand more, the workload becomes humanly impossible and reaches an implosion, a critical point. All of a sudden, you've failed. Your unlimited desire for your goals has outpaced both your emotional and mental limitations. Now because you're so mentally exhuasted you can't even manage to 'try your best'. The self-sacrifice that you do when you exhuast yourself only lessens your true potential. Was the self-sacrifice that got you small gains in the short-term really worth the long-term achievement? Aren't your goals a marathon, a long haul, a place that takes hours upon hours to reach? If you want better, you need to understand this. You don't heal a wound by trying to build a higher pain tolerance, you address the root issue. You need to dismantle the self-hate, because if your thoughts truly affect how you mentally and physically behave based on actual scientific evidence, then the self-hatred is not even helping in the first place. Doing all the 'self-sacrifice' and destructive nature is useless. You won't ever be able to achieve what you want if you're not able to show up in the first place. This is the best advice I can give from my own perspective, but you really want something worth your while then see a therapist.