When your AC quits in the summer, we may not always be able to be at your home within the hour. A few things you can check before you call:
Change the batteries in your thermostat. Even if the numbers on your digital thermostat look clear and solid, the batteries may be dying.
Change your filter. An Air Conditioning system will not perform properly if it is being starved of air by a dirty filter.
Check your breaker. Most of the time, if a breaker trips, there is a reason and it will not stay reset. Sometimes though, an irregularity in the power supply or some other issue that resolves itself can cause a tripped breaker.