And He called to Him the crowd with His disciples and said to them, "If anyone would come after me, let him deny himself and take up his cross and follow Me." (Mark 8.34)
The invitation from Jesus to everyone - the crowd and those who had already committed to Him - is to deny self, die to self, and follow Jesus.
Some people think that discipleship is the second step in a relationship with Christ, as if it is reserved for super-believers in Jesus. Not according to this text (and many more in the NT).
That is the essence of Christianity, not the add-on.
But that's just me thinking thoughts...