I've been playing online for 9.5 years now and this has been a consistent problem for me. I'm a long-run winner but still can't seem to push myself for hours on end when things are going well. I'm now grinding Spin&Gos, and can play for 6 hours with relative ease at the 7$ level, but when I play the 15$'s I could be for example +150$ in an hour and my mind can't help but wandering towards calling it quits; it's only when I'm losing or breaking even that I seem to be able to keep chugging along. To be sure, a 150$ isn't a huge swing for me given that I have about $10K roll, and have dealt with countlessly many swings of that size or larger over the years, so I think what is really stopping me is the fear of being proven that I'm not good enough to win over the long run.

Anyone else have these problems, and what do you do about them?

this is simply a mental block you allow to exist. you are failing to maintain a consistent positive attitude and mindstate. you don't physically change when circumstances change(winning big or losing big), you mentally change. Think deep to your self and you should be able to find out what triggers this lack of motivation and confidence when your results change. this a mental battle that you have away from the tables and it will rear its face in different aspects of your life. side analogy, I was once told that life's biggest battles are won and lost between the ears. (brain being whats between the ears)

you need to get out of your comfort zone and openly fail despite your efforts. accept your failure and come up with an honest plan to constantly learn and improve. once a person becomes content, they will slowly regress. strive and you can and will prove lots to yourself. last but not least, if you worry about results and not making the most +EV plays you will crumble. nothing kills EV like being unsure and scared. this is the mindset behind trumping downswings. play to your best ability 1 hand at a time.

Solid

You sound very risk adverse. 10k bankroll and grinding $7s LOL!

You could stop looking at your bankroll while you play. The reasoning of playing or not based on bankroll is a mistake. If you're chasing losses and not playing your A game, it's an error. Likewise, crushing the game and leaving while you're playing your A game is an error.

Cashout 9K of your roll, take a break and then run it up again.

its fear based.

Sure enough, but what to do against it?

keep a healthy roll if your playing spins those things have super crazy variance.

How about playing a format you could get staked for. they would require a minimum time spent playing.