You should worry if a breaker trips as it can be a sign of a short circuit, bad wiring or other electrical issue that needs repaired.
However in some cases a breaker may simply trip because you overloaded it and then once you remove the overloaded electrical appliances from the circuit then the breaker can safely be reset.
A tripped breaker cannot cause a fire as the tripped breaker means the electricity has been shut off to the circuit.
The breaker is designed to trip in the event of an overload or short circuit and so there should be no fire danger.
However a wire that continues to heat up or outlet that heats up can cause a fire.
It's not safe to keep resetting a breaker that constantly trips as you likely have an overload of the circuit or you have a problem with the circuit that needs fixed.
The breaker is detecting a problem such as an overload or something bad with the circuit and it trips to protect you from a fire.
You should immediately reset a tripped breaker and find out what tripped it.
However if the breaker trips again then you should leave the breaker off and find out what is causing it to trip as the breaker is there to protect you and your home from overloads and electrical fires.
If the circuit breaker trips it means there's either a short circuit or an overloaded electrical outlet or circuit.
Tripping a breaker once in awhile does not damage it.
However repeated tripping of the breaker constantly damages the breaker and wears it out.
Although a breaker is meant to trip it should only trip when there's an overload or a fault in the electrical circuit and if the breaker keeps tripping when you reset it then there's either too much load on the breaker or a loose wire or bad connection somewhere.
So if you reset the breaker and it trips again then you should leave the breaker off and call an electrician or find the problem yourself if you're comfortable working with electricity.
A circuit breaker that trips too often is and indication of either a problem with the circuit breaker itself or there is an overload or short circuit on the circuit it protects.
Either way the cause needs to be determined as any poetential fault could pose a fire or shock hazard.
Thermally tripped breakers get weak when the contacts oxidize causing extra heating due to contact IR loss.
In effect the contacts preheat the bimetallic bender so that it takes less heat due to current to cause it to trip.
If you want to force a circuit breaker to trip without risking your property, turn it off through the panel.
You'll need to plug in an appliance or turn on lights that are connected to the circuit and the corresponding breaker.
Afterward, you need to manually turn off the breaker from the panel.
Most circuit breakers are rated for around 2000 operations or 2-3 fault interruptions before they should be reconditioned.