A disciple is one who emulates the life of Jesus here on earth, one who had made Christ his role model. Such person is more concerned is doing the will of Jesus more than anything else. We see how Peter and the rest of the disciples followed Christ everywhere He went.
The crowd surrounded Christ because of the healing, miracles and other things that they could get from Him. But the disciples were not really after all these things. That's why even after the multitude left they still remained by the side of Jesus.
Matthew 19:27 (AMP)
Then Peter answered Him, saying, “Look, we have given up everything and followed You [becoming Your disciples and accepting You as Teacher and Lord]; what then will there be for us?”
Becoming a disciple of Christ means forsaking all. We have to go all in and make Him Lord over our lives. These means keeping his commandments. We can't afford having one leg in and putting the other outside.