Hebrews 6:4-6, AV...
4 For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost,
5 And have tasted the good word of God, and the powers of the world to come,
6 If they shall fall away, to renew them again unto repentance...
"Repentance" is a MIND word: meta (g)noia, meta MIND, after-mind, change-mind, which is very imnportant here; because, having a new mind, the mind of Christ, and then falling away, another new mind is not going to happen. There is recovery at this point, as best as I understand. One must change behaviour, bringing it back in line with Christ and the gospel. In the subsequent vs.7-8 the rain is used to illustrate
"But that which beareth thorns and briers is rejected, and is nigh unto cursing; whose end is to be burned." (Hb 6:8) Some serious weeding is on the agenda. Those are what are making the land unfruitful, "the cares of this life and the abundance of riches" according to Jesus.
A little later He points to Abraham's patient endurance to obtain the prize.