Why a breaker keeps tripping, and when to stop resetting it

A breaker trips when more current flows than the circuit’s wire can carry, or when it detects a fault. Either way, it is protecting the wiring behind your walls.
If it trips when the kettle, the microwave and the toaster run together, that is an overload: move one appliance to another circuit and reset the breaker once.
If it trips with almost nothing switched on, or straight after a reset, leave it off. That points to a fault in a cable, an outlet or an appliance, and it needs an electrician.