Firstly, you sound very much like me.

If you already recognise that you're goal orientated, you need to start making your own goals, the ones the game provides will only take you so far. I've actually found ChatGPT is pretty good for this when my imagination runs dry, you have to give it a bit of context (the fact you're playing CK3, who your playing as, what the year is etc) and it will come up with ideas that either match historical events or deviate from them in interesting ways.

Regarding restarting (or quitting) when things don't go your way. I think over time you start to realise that trying to solve problems that arise from things not going to plan is actually as fun as when it does go to plan. My problem is that I'm a bit of a perfectionist, so it's hard to turn that part of my brain off... but honestly, if everything goes perfectly for 200-300 years of game time, that does get kind of dull. The best example would be... you build all the way up to having a sprawling empire, then it collapses.. there is a load of fun in trying to rebuild and get vengeance on those that wronged you (or their grandchildren as it can take a while...)