Hebrews 6:4-8 NASB
For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, and then have fallen away, it is impossible to renew them again to repentance, since they again crucify to themselves the Son of God and put Him to open shame. For ground that drinks the rain which often falls on it and brings forth vegetation useful to those for whose sake it is also tilled, receives a blessing from God; but if it yields thorns and thistles, it is worthless and close to being cursed, and it ends up being burned.
This passage calls into question the belief that "once saved, always saved". Jesus tells us that no one can be snatched from His hand, but here we get the sense someone could wander away on their own. We could cause Him to spew us from His mouth.
Falling away describes the receiving of salvation of God that bears no fruit. Though connected to the vine, fruit does not appear. There is no evidence of life taking root in that person. This life devolves into thistles and thorns, which will eventually be gathered and burned, like the worthless servant who buried his talent in the ground. If we see the light but keep it hidden in the miry clay of our lives, it will be taken from us.
In Revelation we see warnings to several churches to repent and turn back to God. He is merciful and slow to anger, but there is a growing season and a season for growth. He warns us to return to our first love or He will come and remove our light stand.
Don't bury it, let it shine.