"And everyone who has left houses or brothers or sisters or father or mother or children or lands, for my name's sake, will receive a hundredfold and will inherit eternal life."
The promise of Jesus to His followers is of eternal satisfaction, not just temporary reward. Jesus gives His disciples this assurance: it is well worth any personal sacrifice to follow Him. And that promise extends to those who follow Him today.
There are sacrifices both material and relational that we must make to truly commit to following our Master. Jesus mentions the physical cost of houses and lands. No material asset should keep our hearts from Him. In the immediate context, Jesus has just seen the wealthy young ruler walk away from Him because he could not turn from his possessions (Matthew 19:16-22). Peter remarks that Jesus' disciples have left it all on the gamble of Jesus' kingdom. And that was true. Love any earthly possession and you cannot truly love Jesus. You are blessed by Him when you possess only Him.
Relationships also change. We cannot love any person more than the Lord, for it would make that person an idol. And Jesus warns that even the closest of family relationships is "left" to follow Him. Jesus must have my heart in order for me to be His disciple. It is more than just "learning". Those who only define a disciple as a "learner" miss this. Discipleship is a commitment to the core of what I want or what I love. And it is rewarded by Jesus intensely if I truly commit to being His disciple.