I used charge hourly years ago. I had the same problem where taking a holiday made me think about losing money. Now I charge a monthly rate based on the number

I used charge hourly years ago. I had the same problem where taking a holiday made me think about losing money. Now I charge a monthly rate based on the number of days a week I work (roughly equating one month to 4 weeks, granted they're not but it makes life easier). Now I don't worry about taking time off because once I've clocked my days for that week I'm done I won't get paid more. It also means you know exactly what your income will be each month which is handy for budgeting.