If you are a fee based earner, or commission only earner how do you stop worrying about the uncertainty?

I have always earned commission. So of course each month is a new month with the thoughts that follow that. “Will I earn enough this month?”

Some people run their own businesses and also do not know their earnings each month right? As do some fee based earners. I want to know how I stop this overwhelming me totally? I have worried for 15 years and I am exhausted. I wonder how others cope with this type of uncertainty, perhaps they do not focus on it so much as I do? at the expense of almost having no life due to worry. Or have I just lost the plot? I probably just need to “get things into perspective by similar issues shared with other people and their ideas on it. I can’t change jobs either.