Okay, I'm going to be a bit hard on you, so prepare yourself.

This is all part of being an adult.

Point #1 You need to know the requirements of your bank as far as minimum balance, when deposits are credited and available, fees that can be charged and for what. It's their bank and if you want to use it, you have to know the rules. I know that wasn't the problem but in the future, it could be.

Point #2 It's addition and subtraction. That you can handle. That's why you have the credit and debit portion of the checkbook. Use it, then check your calculations. Nuts to the idea of adding something extra to the amount when you write a check. You'll never be able to balance a checkbook that way. By the way, balance it. That way you know how much you have based on the checks that are written, not just the ones that have cleared. That was the problem.

Point#3 Don't live paycheck to paycheck. Have a little extra built up.