Eventually, someone will operate a blow dryer or another high powered appliance on an already overloaded circuit once too often, and when you trudge down to the breaker box to flip on the breaker again, nothing will happen.
The mechanism inside the breaker is not made to be tripped on an ongoing basis, and may eventually wear out from overuse. Luckily, circuit breakers are relatively easy to replace.
What you will need:
A circuit breaker
Residential electric circuits for general use will use either a fifteen or twenty amp circuit breaker, depending on the line. Your breaker will have either a "15" or "20" stamped on the breaker switch so you will be able to determine which breaker to buy by looking at the defective breaker.
Before going to the home improvement store to buy your breaker, write down the name of the manufacturer of the breaker box. This is important, because breakers do not fit universally in any breaker box. There are subtle differences in design, even though they are roughly the same size and serve the same purpose.
If your breaker box is old, or the manufacturer discontinued the model and no longer sell breakers to fit the box, ask the salesperson for an after market equivalent. There's a good chance that other homeowners in the area have the same model and have experienced the same problem, so an aftermarket equivalent may be available.
If all else fails, you could bring the old breaker to an electrical supply store, and they can find a comparable breaker.
Screwdriver and flashlight
You'll need these items for replacing the breaker.
Installing the new breaker
Keep your supplies close at hand (especially your flashlight) and turn off the main breakers to your home. All of the electricity will be turned off, so you should warn family members in advance.
When the power is off, you can access the breaker box. Never try to work inside the box when it is powered.
You will begin by pulling out the defective breaker. You will need to pry it from the outer edge first (on the side where the black wire is attached. If it doesn't come out easily, persuade it slightly by slipping a flat head screwdriver under the rim, then pulling it out of the slot with your fingers.
When the breaker is out of the slot, disconnect the black power wire from the screw terminal with your screwdriver.
Next, attach the black wire to the identical terminal on your new breaker. Then, slip the inner end of the breaker (opposite the black wire end) into the slot, and push the outer end in until it you hear a click and the breaker is flush inside the slot.
Turn on the main breakers, then turn on the new breaker, and you're finished.
While this solves the problem of the broken breaker, it won't keep the breaker from being tripped constantly from the line being overloaded. You should consider hiring an electrician to add an additional line, which can be used solely for a blow dryer or another high powered appliance.