how much relaxation help us ?

You need a balance between rest and relaxation and doing physical activity. Your body knows when it needs rest and sometimes we don't rest when we should which runs down our immune system and weakens it making us prone to illness and accidents. On the other hand we pretty much know when we feel rested we should get up and doing and should plan things to do and do them. Both make you feel great as long as you don't over do one or the other.