I'm 39, self-employed and most of my work is deliverable-based - i.e. I agree an fee and a timescale at the beginning and get paid once that deliverable has been signed off (or sometimes at agreed stages if the deliverable is some way off).
If I choose to work for 4 clients at once and spend some of my time on the internet, then it just means I have to spend some of my internet time on client work. The amount of work I do won't change it'll just be 'time-shifted' - and I've never failed to meet a target, and never had any need to 're-baseline' any target either, nor have I ever tried to wriggle out of a contract.
If I don't work, I don't get paid. I don't get sick pay, I don't get holiday pay, I don't get paid 'family' days, I don't get my pension paid for, I don't get my health insurance paid for, I don't get my public/employer/professional liability insurance paid for. It all comes out of my fees.
I'm not technically adept enough to do anything other than minor repairs & servicing on my cars (well did do a head gasket on a VW Polo once), and don't trust the dealers, so pay a trusted independent & ///M specialist to do mine for me.