If it wasn't for Ebony and Tigger I'd be seriously wishing myself to disappear one day.

If you are trying your best, the only person you should need to prove anything to, is yourself. Everything I do someone else can do better. It did used to bother me when I ad this, people not accepting that anything I did was good enough. The turning point for me was finding my strength to say it was good enough, that the problem is with the other people that criticize.

It's difficult to do, but ignoring the bad comments is necessary. Know that you are good enough, you have value and pride in what you do yourself. People that talk like that are not worth the time.

That's not your fault. If I were you, I wouldn't blame myself.

Like say for example at work it feels like I can't win. If I'm too fast I miss stuff and get in trouble for missing stuff and if I'm thorough I'm too slow and get in trouble for being too slow.

That's not your fault. That's called a Double Bind or Learned Helplessness. It's a breeding ground for mental illness. Perhaps send an email to your supervisor describing the problem.

Many people at work have voiced what's happening and nobody cares.

I mean, I know from others (on forums) that I am too hard on myself, feels like I'm not hard enough on myself though.

How would you benefit from being hard on yourself?

Because in theory it gives me a big kick up the arse.

And in practice?