Ps 21:1 The king shall joy in Thy strength, O Lord, and in Thy salvation how greatly shall he rejoice!
:2 Thou hast given him his heart's desire, and hast not withholden the request of his lips. Selah.
:3 For Thou preventest him with the blessings of goodness: Thou settest a crown of pur gold on his head.
:4 He asked life of Thee, and Thou gavest it him, even length of days for ever and ever.
:5 His glory is great in Thy salvation: honour and majesty hast thou laid upon him.
:6 For Thou hast made him most blessed for ever: Thou hast made him exceeding glad with Thy countenance,
:7 For the king trusteth in the Lord, and through the mercy of the most High he shall not be moved.
:8 Thine hand sall find out those that hate thee.
:9 Thou shalt make them as a fiery oven in the time of thine anger: the Lord shall swallow them up in His wrath, and the fire shall devour them.
:10 Their fruit shalt thou destroy from the earth and their seed from among the children of men.
:11 For they intended evil against Thee: they imagined a mischievous device, which they are not able to perform.
:12 Therefore shalt Thou make them turn their back, when Thou shalt make ready Thine arrows upon Thy strings against the face of them.
:13 Be Thou exalted, Lord, in Thine own strength: so will we sing and praise Thy power.
While Ps 20 was sung when the army left to go to war, this one was sung at the return. It was sung a lot because God gave David many victories.
Everything in this Psalm whether about David or the Lord can be said about the Lord.
We must remember we battle spiritual battles daily and that Psalm 20 tells us God fights for us. We are called into the battle also. Once we win that particular battle (cause there are always more), we rejoice with Psalm 21.
Ps 62:5 My soul, wait thou only upon God; for my expectation is from Him.
:6 He only is my rock and my salvation: He is my defence: I shall not be moved.
What cheers you up? Is it your job, possessions, family? That's the problem. We know God is so vast everything else is nothing in comparison. Yet we are not happy because our minds are set on things. We multiply and beautify things. We put our confidence in things and God, our job and God; husband and God; home and God. So we put God as a plus sign after something else. God is never happy when He is put second.