Ive always had a full time job, I bought my first window round 18 years ago when 9/11 took hold and I thought I was going to lose my main job so did this as an add on. Ive now built that round to nearly 1000 customers and have 3 people working for me. Its very hard going as I still do a bit myself as I work shifts.
Ive spent weeks doing windows alone and it does have its good and bad points however nothing some music or a podcast doesn't sort. The lonelyness can get to you if you work alone and its very hard to keep motivated however my other job also reminds me of how good it is to work for yourself and also work outdoors.
I won't comment on the mental health side as I'm not a trained medic nor do I actually know you, what I will say is go and see your DR and explain your issues