Behaviour is defined as how one acts or carries out oneself. For example the way you communicate is behaviour whereas vital behaviors are those behaviors that if not adopted can lead to disastrous consequences. For example doing crucial conversation is vital behaviour.
According to a research if you set rules for yourself regarding facing any sort of a challenge the chances are high that you will act appropriately in crucial moments and that is why not the behaviors but vital behaviors are advisable. If well before time you have prepared yourself and you know what vital behaviour is necessary in what situation, you will act in accordance when in crucial moment.
For example maintaining your sugar levels (Crucial moment) asks for injecting the insulin in your body (Vital behaviour), proper diet (Vital behaviour), and exercise (Vital behaviour) regularly. So if you are well prepared for crucial moments, it means you have learnt the vital behaviors required to tackle the situation.