I burned out working my ass off nights and weekends because my previous partner was absolutely sure he'd be able to sell our product. Which unfortunately turned out different (but that venture still makes money... Too much to let it die... Too less for it not to be a pita)
'your startup chances increase with a partner'. Yes, but I'm not interested in a startup that makes me filthy rich, I'm just looking for something to replace they daytime job where I don't have to be at an office 5 days a week and where the office can be wherever my laptop is.
I have built several succesful applications over the years (for others) where I used my UI/UX skills (and really just common sense and thinking before code/design). I can make the tech side of a project from A to Z (and in my current daytime role also doing sales and marketing as I'm the sole manager of a very small but very profitable company).
And next time I'm taking on a co-founder, I want proof that he has commercial skills because it seems anyone thinks they can do marketing and sales or that it will happen by itself or something.