Make a really good and detailed budget based upon your needs/life style. Make a complete list of your monthly income/expenses. Whatever remaining you have to figure out how much you want to save/invest/spend. I have my savings to be enough to cover my monthly bills for 6 months in the event i lose my job/cant work.

Since thats at a comfortable amount i set aside 1/3 of the remaining cash for unknown/sudden bills (car issue, drs copay etc), 1/3 to replenish my savings account or invest and 1/3 on myself. If at the end of the month there were no unknown bills then i see how im feeling. Maybe i dont want to go out and ill save extra or maybe ill buy myself a small treat. Maybe ill set it aside towards a larger gift for down the line.