Splitting irregular freelance income between bills, taxes and savings

Freelance income arrives in lumps. One month I get paid for three projects; the next is almost quiet. I used to treat a big payment as extra money, then panic when tax and insurance bills arrived. I'm now thinking of separate accounts for taxes, fixed bills and savings, funded by a percentage of each invoice. For people with irregular income, do you pay yourself a stable monthly amount from a buffer, or adjust personal spending as payments come in?