Quick answer
A permanently soft heart is called happy. The contrast is not reverence against irreverence but softness against hardening.
Read both lines
The opening word is אַשְׁרֵי, the beatitude particle that begins the Psalms, the same form 20:7 used, so this is an observation about a fortunate condition rather than a promise. The word rendered "reverent" is about a sustained carefulness, a man who keeps taking things seriously, and the always is the load-bearing part.
The second line names the alternative as a process rather than a state: hardens his heart, present tense, something he is doing. That is the verse's real contrast. Nobody decides once to be hard; it accumulates, usually through small refusals to be moved, and the calamity at the end is presented as the terminus of a direction rather than a punishment dropped on him.
Related: Proverbs 20:7 · Proverbs 29:1 · Proverbs 14:16 · Proverbs 16:20
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.