I lost a lot of weight but gained 90% back. I feel like a failiure?

You are not a failure. There is no such thing.
In programmer lingo, we like to refer to bugs as "undocumented features". I'd like to think it's more than mere optimism or salesmanship, but rather that through these we glimpse true insights of the code's essence and what it means to others. Sometimes the effects can seem quite remarkable even to the writer.

I'm not trying to say this in a bad way, but you aren't in full control of your mind, technically. As research shows, your conscious cerebrations' usage percentage is in the single digits. The rest is reactive to circumstance. Bereft of this trait, seems to me you'd be more akin to an automaton than human, discarding memory to achieve a task. Efficient, at a terrible cost of losing your self. But I digress.
Now, whilst some of these processes constitute the regular flow of life, sometimes you have these demons taking hold, making demands which make you miserable in the long run. You have the gift of being able to expose them, and thence to object to their influence. They are strong, deeply ingrained, and can sense weakness. If you just go there and attempt to uproot them, they will likely use it against you. You need allies, people who will protect your blind spots. You need stratagem, a plan of attack to handle the sort of unforeseen situations thrown at you. Above all, you need to be courageous & indomitable in spirit. This is difficult, no doubt, but there's an effective tactic: if there is no refuge, no means of escape, pressed against the wall, the only way is forward. Accept that the only way to peace & change goes through facing these fears.