Something that helps is have someone drop you off at the gym and tell them not to pick you up until three hours , or however long you like, has passed.

If you are stuck in the gym for hours, you will (or strongly might) find a way to just keep at it. I meander around very slowly and take my time and just keep going over the same thing if I have to. I go when no one is there.

I hope you can keep going. You are brave to try!