In response to learning about how even some of the Greeks want to learn about Jesus, Jesus talked about how his time has come, especially the time where he would soon die on a cross on behalf of humanity. But then Jesus links that hour to a pretty big call.
Jesus proclaims that people who love their life lose it and people who hate their life would keep it (12:25). According to the Interlinear, the Greek for "hate" (Strong 3404) has been used to refer to "love less", and based on the context (as we'll see shortly after), Jesus is referring to priorities and service. In particular, "loving life" means focusing more on one's desire, while "hating life" means focusing more on loving God and loving neighbors than oneself. In fact, from Jesus's statement, selfishness and selfish pleasures do not last, while a renewed attitude in focus on loving God does. Faith Alone made further explained the use of loving/hating life in this article.
Then Jesus talks about service. He talks about how if anyone wants to serve Jesus, the disciples should let them follow Jesus, and the servant would be honored by the Father (12:26). While eternal life is received upon belief (as stated in John 3:16 and 5:24), focusing on God rather than oneself is how we activate our abundant life in our present life, and one way to focus on loving God and other people more than ourselves is serving God. Serving God is part of discipleship (AKA "following Jesus") and results in honor from the Father.
For those who believe in Jesus as Lord and Savior and are new to discipleship, a great next step is following Jesus in service. Following Jesus involves a lot of self-sacrifice but results in great honor from the Father and an abundant life.