Following God / the Lord Jesus, is not a religion, tho much religion has been constructed that makes this claim. Religion is a system, and religions systemic, whereas following the Lord is centered on Him, the Living God. As such, these systems have complexities, principle tenets, etc., and create assurances based on adherence to regulations. As Christ's followers, assurance doesn't come to us in that way.
We, as believers, are assured in God's grace by following Him and obedience to His will. This requires seeking Him, and is a living dynamic. There is abundant confusion about this, and we can all easily veer off the highway of relationship with the Living God into the ditch of religion, sometimes without even noticing. It's easy to stumble in this way. I've done it.
If we see it as it is, however, I think we can observe that the Lord didn't come to establish a religion. Let's don't minimize His work by thinking of it in this way. Religion is man's work, and man's domain. Jesus is not just another guru on the guru landscape, tho that's what the spirit of the age tries to display Him as and that is the Jesus that religions espouse, those that recognize Him at all. WHo is He? Jesus Christ is the risen Son of God, and His truth stands in sharp contrast to the other voices that attempt to compete. You do not have to acknowledge this for it to be true, as He is Truth embodied and personified.
Lord, help us to hear Your voice and follow You thru this crowd, as You promised we could, and as we promised we would. Don't let us draw our assurances from forms and rules, but from You and You alone.