Thanks! Will do 
Yes I'm familiar with this feeling, like you I find it difficult to predict. What I do is definitely take off time which has to be taken, for instance if there's a course or concert that I really, really have to attend I'll do it.
I currently am starting work in my other profession, which pays a lot less for a similar amount of work if not more, and it's a list something very new to me which makes me very anxious and not want to do it. In other words. I'm in that place where I'm worried that the lower paid work will get in the way of my availability for sex work bookings which is where I make the money which allows me to fund things for my other business.
This isn't a thread about other forms of work, my post is about those dilemmas over bring self-employed.
What I try to remember is that it's all investment in me whether it's time off for the sake of it, or time off participating in further qualifications, training that sort of thing.
Also remember that a booking isn't a booking until it happens.