Life has unexpected expenses: car or appliance repairs, for example. It may be helpful to create a rainy-day fund in a separate checking account for small financial shocks like these. Also create an emergency fund which should have enough to cover an unexpected job loss or serious family health issue.
Many financial experts recommend setting aside as much as 9 months of living expenses to keep you afloat during emergencies, but you can certainly start smaller, with a goal of socking away 2 months of salary.