I'm finding it difficult to understand your post. Perhaps the word assertiveness is confusing me somewhat.
However, I gather (guess) you are having problems maintaining any positivity you have on a consistent basis. Having positivity present is a major bonus in life as it is and good for you that you have such periods.
I'm 63yo but at the youngish age of 26yo I attended a motivation speech that changed my life. You can read it here
Google-- Beyondblue topic 30 minutes can change your life
From that moment on I was motivated except for a few short periods of depression due to, at the time, unknown mental illness.
Fast forward to around 1999 and I was commencing my own investigation business. I had to rise early often 3-4am and get motivated. So I developed a plan. I knew having a hot shower tended to wake me up as did at least a muesli bar on the way to work some 2-3 hours away depending on location. Once at work I'd go for a brisk walk. Then I was fully awake for the days events. This ritual was also set in stone because I knew if I slept in I didnt get paid for the day and bad habits are hard to shift.
But there is more to such a routine. Adjustments must be made like knocking off work early and/or an afternoon nap etc otherwise you fall in a heap eventually and that occured for me in 2013 and I havent worked since, sadly.
Your issue with your car needs to be resolved. The matter is annoying you and causing you untold frustration. You could give her time say one week to resolve the matter because your freedom of leaving the house to do whatever you need to do is essential. She might need to attend a bank like others do in order to secure her own wheels.
BTW, I used to have two alarm clocks, one beside my bed and one in the hallway. If I snoozed the close one the other would drive me nuts until I got out of bed. I hope that helps.