Exactly! Your business can be a threat to your emotional wellbeing, but your emotions are definitely a threat to your business as well. If you're alone then there's nobody to stop you from following your whims. It's very alluring to do what you _want_ rather than what you _should_. A team has a sort of inertia in that there's pressure to not let the others down, and changing course requires that more than one person wants to do that.

I think solo founders (including myself) should ask themselves: why are you solo? If you (like me) want co-founders but can't find any, maybe your idea isn't so great. If you prefer to be alone then scouting customers may not be your strength.