Drive to ground, meet Secretary, check field, get changed, warm-up, check teamsheets, kick off ... for normal games, no mental prep required.
For higher profile games, e.g. relegation/title deciders, finals, etc. something like yours. I had a pre-match playlist and a post-match playlist. I would also consider scenarios in my head and prepare how I would deal with them should they occur.
Rarely needed to mentally prepare though as I was constantly thinking about refereeing (even at work). Seems to have subsided a little since I hung up the whistle at the end of last season.
I like that you have goals in your signature. I notice they are all outcomes. What are you going to do to achieve them?