I think the OP nicely pointed out the whole context of the passage is spiritual maturity, not losing ones' salvation. Remember, there are no chapter divisions in the originals.
Hebrews 5:11-14 KJVS
[11] Of whom we have many things to say, and hard to be uttered, seeing ye are dull of hearing. [12] For when for the time ye ought to be teachers, ye have need that one teach you again which be the first principles of the oracles of God; and are become such as have need of milk, and not of strong meat. [13] For every one that useth milk is unskilful in the word of righteousness: for he is a babe. [14] But strong meat belongeth to them that are of full age, even those who by reason of use have their senses exercised to discern both good and evil.
Hebrews 6:1-6 KJVS
[1] Therefore leaving the principles of the doctrine of Christ, let us go on unto perfection; not laying again the foundation of repentance from dead works, and of faith toward God, [2] Of the doctrine of baptisms, and of laying on of hands, and of resurrection of the dead, and of eternal judgment. [3] And this will we do, if God permit. [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; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.