A man is said to have a life on its own when the man has free will. Freewill is what determines whether one has a life or none, i.e Robot toys although they can move because of battery, they don’t have life on their own because those toys have no self will
The self which is us has a life on its own in a sense that, the self has a free will capable of deciding and choosing on its own.
But, the one who gives life which is the spirit has a separate will than ourselves. The spirit follows God’s will because that is the part of God that is in us, it is the Creator’s breath (Gen 2:7) and without it, ourselves would not even exist.
But, although our spirit follows God’s will it does not intervene with our own will so that, we are free to choose between following the will of the spirit within us or not. The spirit is there to give us life and not to intervene with our will but, let’s not take it for granted because if we do, it may not always be there to give us life after experiencing physical death.
This is the reason why Jesus said in Matthew 25:42-45 that if we help the helpless, we have done it to Him also because the life that runs through them is part of Jesus who is the vast eternal life. If we love God or Jesus and we know who He is and what He is, surely, we’ll love our neighbor as we love ourself because the life that is in us and them is part of the vast eternal life who is Jesus.