Okay, number one thing to keep in mind: you're lethargic and "blah fuck this why even do it" right now, but 10 years down the line you are going to thank yourself for pushing through this and doing what needs to be done. Sometimes life sucks and you get stressed out and don't want to follow through with something because it's irritating and you know you can cop out, but you need to think ahead. Where are you going to be in life without a degree/a good job? Think about the money troubles you're having now, and then multiply it by 10 years when you have to pay rent and gas and electric bills and food and everything else. A degree is going to play a huge role in setting yourself up for a comfortable life, so even though it sucks now and your own "sense of achievement" now feels like nothing, you have to be mature enough to look past that and think about your future. In terms of the audition: if you think you aren't going to get the part, you won't. Simple as that. Plus, if I were the director and you tried out and didn't put 10000% effort in because you didn't think you'd get it, I wouldn't cast you anyway. You need to totally throw yourself into the role and believe that you'll get it, because confidence is attractive and it shows. Show them that you absolutely deserve the part, and your chances of getting it are going to skyrocket.
Of course it's worth it all. Everyone goes through rough patches, and feels like things are crashing down on them. You need to just tackle things one at a time. Break things down into manageable chunks and deal with them that way instead of looking at the big picture. Good luck.
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when i play doctor, i play to win