This is due to the thought processes that emerge when we encounter an incident. The thoughts lead us to feelings and actions. The problem arises when one gets caught up with a negative thinking pattern as this leads to negative feelings and dysfunctional behaviour. Each then reinforces the other, creating a vicious cycle. In order to break this cycle, the negative thoughts needs to be replaced with more positive, rational thoughts.
Negative thoughts are usually automatic and have their basis in previous experiences.
A conscious effort to slow down this automatic response is required. This can be done by first identifying what the thought is. Negative thoughts are usually irrational and these questions will evoke thoughts that are rational and positive. The minute another thought emerges the subsequent feelings and behaviour will change. So you may realise that the restaurant is extremely busy and many other tables are kept waiting too.