Some context is need here. All commentaries seem to agree that this is a Psalm of David and that it was written when he was on the run from Saul. There are three distinct divisions within the Psalm:
v. 1-10 David prays for Safety – In the opening verse David prays that God would Contend and fight against those who would harm him. Note he closes this section, and each with words of Praise my soul shall rejoice in the Lord… “Lord, who is like You
v. 11- 16 David complains of his enemies – This is not to be misconstrued as whining but a righteous prayer for salvation from his enemies. Malicious witnesses rise up…They repay me evil for good, I think we have all faced challenging times when it seems like evil abounds around us. The good news is that God hears our pleas and if it be His will, will answer our prayers.
v. 17- 28 David calls upon God for help and support – When desperation seems to set in DO NOT call 800-Phone a Friend. Your real hotline for help is God and David knew that. v.17 Lord, how long will You look on [without action]? Rescue my life from their destructions…
The key if you will to this Psalm is found at the end of each section, Praise for God. Again, while most commentators agree the general theme has to do with facing enemies, opposition, or something of that sort. Yet one cannot hope to do that apart from in the case of David God, or in our case Christ.
“My tongue shall speak of thy righteousness and of thy praise all the day long.” See now I have made a discourse something longer; ye are wearied. Who endureth to praise God all the day long? I will suggest a remedy whereby thou mayest praise God all the day long if thou wilt. Whatever thou dost, do well, and thou hast praised God. When thou singest a hymn, thou praisest God, but what doth thy tongue, unless thy heart also praise him? Hast thou ceased from singing hymns, and departed that thou mayest refresh thyself? Be not drunken, and thou hast praised God. Dost thou go away to sleep? Rise not to do evil, and thou hast praised God. Dost thou transact business? Do no wrong, and thou hast praised God. Dost thou till thy field? Raise not strife, and thou hast praised God. In the innocency of thy works prepare thyself to praise God all the day long.—Augustine.