God, the supreme power has given us the opportunity to Neutralise the good/bad deeds which we have done since past births. For this the almighty has gifted this precious life to wash up and clear the balance in our accounts which is getting accumulated since ages.
For washing up, one has to follow the path shown by the god for clearing the deeds. This can be done by enchanting the name of God in all good bad times during stay at earth. This stage when completed is termed as Salvation.
The speed for clearing the deeds and attaining salvation is a very slow process for a Soul. So the soul requests the god/messenger of god to send them in a live form (human) where the process for Salvation is fast. As human form is the only form which is subjected to perform Karma however other living things can not perform the same.
Every soul before taking birth in human form promises the messenger that they will follow their steps and clear out their accounts rapidly. But after entering the materialistic world most of the soul forgets the main aim and they starts accumulating deeds whether positive/negative.
Due to the above fact the soul has to take repetitive births for zeroing the outcome of the deeds performed and spending too much time in living form. It is must for every human being that they try to fulfil the promises they made to the god and dissolve themselves in the holy feet after attaining salvation.