The "fear" here is not so much reverential awe, as anxious, or "nervous" sensitiveness of conscience. To most men this temperament seems that of the self-tormentor. To him who looks deeper it is a condition of blessedness, and the callousness which is opposed to it ends in misery.

Happy is the man that feareth alway - That ever carries about with him that reverential and filial fear of God, which will lead him to avoid sin, and labor to do that which is lawful and right in the sight of God his Savior.

Happy [is] the man that (g) feareth always: but he that hardeneth his heart shall fall into mischief.
(g) Which stands in awe of God, and is afraid to offend him.

Happy is the man that feareth alway,.... Not men, but the Lord; there is a fear and reverence due to men, according to the stations in which they are; but a slavish fear of man, and which deters from the worship of God and obedience to him, is criminal, and brings a snare; and a man, under the influence of it, cannot be happy: nor is a servile fear of God intended, a fear of wrath and damnation, or a distrust of his grace, a continual calling in question his love, and an awful apprehension of his displeasure and vengeance; for in such fear is torment, and with it a man can never be happy; but it is a reverence and godly fear, a filial one, a fear of God and his goodness, which he puts into the hearts of his people; a fear, indeed, of offending him, of sinning against him, by which a man departs from evil, and forsakes it, as well as confesses it; but is what arises from a sense of his goodness: and it is well when such a fear of God is always before the eyes and on the hearts of men; in their closets and families, in their trade and commerce, in all companies into which they come, as, well as in the house of God and the assembly of his saints, where he is to be feared; as also in prosperity and adversity, even throughout the whole course of life, passing the time of their sojourning here in fear: and such a man is happy; the eye of God is on him, his heart is towards him, and he delights it, him; his secret is with him, he sets a guard of angels about him, has laid up goodness for him, and communicates largely to him;
but he that hardeneth his heart shall fall into mischief; that hardens his heart from the fear of the Lord; neither confesses his sin, nor forsakes it; bids, as it were, defiance to heaven, strengthens and hardens himself in his wickedness, and by his hard and impenitent heart treasures up to himself wrath against the day of wrath; he falls "into evil" (k), as it may be rendered, into the evil of sin yet more and more, which the hardness of his heart brings him into, and so into the evil of punishment here and hereafter.
(k) "in malum", V. L. Pagninus, Montanus, Tigurine version, Junius & Tremellius, Piscator, Schultens.

There is a fear which causes happiness. Faith and love will deliver from the fear of eternal misery; but we should always fear offending God, and fear sinning against him.

feareth--that is, God, and so repents.
hardeneth his heart--makes himself insensible to sin, and so will not repent (Proverbs 14:16; Proverbs 29:1).

14 Well is it with the man who feareth always;
But he that is stiff-necked shall fall into mischief.
The Piel פּחד occurs elsewhere only at Isaiah 51:13, where it is used of the fear and dread of men; here it denotes the anxious concern with which one has to guard against the danger of evil coming upon his soul. Aben Ezra makes God the object; but rather we are to regard sin as the object, for while the truly pious is one that "fears God," he is at the same time one that "feareth evil." The antithesis extends beyond the nearest lying contrast of fleshly security; this is at the same time more or less one who hardens or steels his heart (מקשׁה לבּו), viz., against the word of God, against the sons of God in his heart, and against the affectionate concern of others about his soul, and as such rushes on to his own destruction (יפּול בּרעה, as at Proverbs 17:20).

Alway - In all times, companies, and conditions.