This time I did some soul searching about what would make me happy. I knew the problem was really with me and though I had strong urges to leave, similar to my previous urges, I managed to stay at my new job for 6 years.
The takeaways from my sample size of 1: You can go back. If you left for some particular reason, it is possible that the situation remains unchanged and you will still be unhappy. If you leave again, you will likely burn bridges so be sure you want to be back. If you are doing this on a frequent basis, look within to understand why you have the need to change jobs so often.
10K higher salary and an extra week of vacation later, I was working there again.
The company lasted another year before it folded completely. I only did it because the boss pretty much left me alone and I didn't have anything to do besides maintain the current system that I built during my 5 years there.
I used this opportunity to start my own company because my daily job took me about 20 minutes in the morning. I previously automated most of my daily tasks. Anyone with any tech experience was fired or let go and nobody really knew what I was doing besides keeping the current system running smoothly.
New jobs are always difficult in the beginning. Mostly because you have lots of unfamiliar systems to learn and new coworkers.
The question you should be asking yourself, is why did you quit your old job in the first place? Do you think anything will be different if you go back?
With the benefit of hindsight I should have raised my problems with the original company, at the time, not just walked away. That would have lead to improvements for myself and others, and saved me a year of starting new jobs which didn't suit me.