You are far from throwing in the towel, as you are here asking for direction. Its very hard to do the solo act - near impossible task you've given yourself and it seems you really beat yourself up about it.

Realize this - most successful ventures/side gigs/startups are not solo efforts and involve quite a bit of luck.

Others have made great pointers for you here. I can only add that maybe you should stop the boom/bust cycle and network to find a co-founder.