It is always proper for Christians to pray for divine protection or deliverance from ungodliness. Jesus, himself, taught us to pray, “And lead us not into temptation, but deliver us from evil.” (Matthew 6:13) 

But our “faith” is tested when it seems that God doesn't hear our petitions. Our Lord was similarly tested in the garden of Gethsemane when he prayed “O my Father, if it be possible, let this cup pass from me: nevertheless not as I will, but as thou will.” (Matthew 26:39) So whatever we pray for, our heart sentiment should be as the hymn “Whatever my lot, Thou hast taught me to say, It is well, It is well with my soul.”

If we are to be footstep followers of Christ, our hearts should desire only the will of our heavenly Father – even if our flesh suffers. Christians are promised that, “All things work together for good to them that love God.” (Romans 8:28)

Perhaps there is a deeper and more spiritual application of Psalms 43:1 for the Christian. The verse begins by saying “Judge me, O God, and plead my cause against an ungodly nation…" Here David is asking God to judge (vindicate) him and compare his life against ungodliness.  This seems to be the same thought expressed in Psalms 139:23-24 when he says “Search me, O God, and know my heart: try me, and know my thoughts: And see if there be any wicked way in me, and lead me in the way everlasting.” Christians must strive to keep their hearts and actions pure and righteous. 

Psalm 43:1 continues saying “…O deliver me from the deceitful and unjust man.”  Every Christian should daily search his heart to make sure that its motives are pure. We don’t want to be controlled by our “old man.” (Ephesians 4:22; Colossians 3:9)  The old man is our sinful flesh. We should constantly pray for help to subdue this enemy of the Lord's people. "For the heart (of the old man) is deceitful above all things, and desperately wicked: who can know it?" (Jeremiah 17:9) 

So Yes!!!  Let us pray daily and fervently and without ceasing that God will deliver us from evil, but with the heart sentiment “For it is better, if it is the will of God, to suffer for doing good than for doing evil,” I Peter 3:17.