Before you even ask, this is not about reincarnation? As Christians, we believe that we pass through the earthly life only once.
But Greek, the language of the New Testament does have a variety of ways of talking about life. St. John like to talk about zoe, the new eternal life we receive from Christ. There is also of course the pneuma, the spirit. But today St. Matthew talks about the psuche, which is the root of all of the psych- words in English. The problem is that it doesn't mean what we tend to think. The mind in the Bible is the dianoia, the ability to know something, literally dia-noia, to know through. The psuche refers to the breath, the breath of life. Sometime it is translated life, sometimes soul. The life that God breathed into Adam at creation. Everything that breaths has this, is given this by God.
When Jesus gives the great commandment in Matthew's gospel we are told to love God with all our kardia (heart), with all our psuche and all our dianoia. Why all these Greek words because we need them to understand what happens at baptism?
When we are created we are created with psuche and dianoia, we are living beings. When we are reborn in baptism we are filled with the Pneuma, and and now have a whole new kind of life, Zoe.
Those who are baptized are not as some would have you think "rational animals", we are something more. Our natural life is not replaced. As St. Thomas would tell us, Grace builds on nature. We have both kinds of life still operating in us.
In today's gospel we hear
For whoever wishes to save his life (psuche) will lose it, but whoever loses his life for my sake will find it.
The great paradox of the Gospel, is that even when it comes to the life God gave us that the moment of conception, we only truly find it when we are willing to let go of it for the sake of the kingdom. Thne we have it all, life to the full.
Today we should be mindful of both lives that we have and nourish them both. As we walk through today, let us pay attention to the operation of all of the parts within us.