Psalm is such a comforting Psalm, and here is Matthew Henry’s commentary (I have bolded a couple of sentences I especially found helpful):
121:1-8 The safety of the godly. – We must not rely upon men and means, instruments and second causes. Shall I depend upon the strength of the hills? upon princes and great men? No; my confidence is in God only. Or, we must lift up our eyes above the hills; we must look to God who makes all earthly things to us what they are. We must see all our help in God; from him we must expect it, in his own way and time. This psalm teaches us to comfort ourselves in the Lord, when difficulties and dangers are greatest. It is almighty wisdom that contrives, and almighty power that works the safety of those that put themselves under God’s protection. He is a wakeful, watchful Keeper; he is never weary; he not only does not sleep, but he does not so much as slumber. Under this shade they may sit with delight and assurance. He is always near his people for their protection and refreshment. The right hand is the working hand; let them but turn to their duty, and they shall find God ready to give them success. He will take care that his people shall not fall. Thou shalt not be hurt, neither by the open assaults, nor by the secret attempts of thine enemies. The Lord shall prevent the evil thou fearest, and sanctify, remove, or lighten the evil thou feelest. He will preserve the soul, that it be not defiled by sin, and disturbed by affliction; he will preserve it from perishing eternally. He will keep thee in life and death; going out to thy labour in the morning of thy days, and coming home to thy rest when the evening of old age calls thee in. It is a protection for life. The Spirit, who is their Preserver and Comforter, shall abide with them for ever. Let us be found in our work, assured that the blessings promised in this psalm are ours.
I love the thought, “Let us be found in our work”–that is our proving ground, putting God first and doing His work…first!