When I'm not sure what to pray for, I usually turn here:
"Our Father who art in Heaven, Hallowed be thy name; Thy kingdom come Thy will be done On earth as it is in heaven. Give us this day our daily bread; And forgive us our trespasses As we forgive those who trespass against us; And lead us not into temptation, But deliver us from evil. "
Oddly enough, something in there usually jumps out at me as appropriate to the situation.
I was thinking more along the lines of this prayer:
How precious to me are your thoughts, O God!
How vast is the sum of them!
If I would count them, they are more than the sand.
I awake, and I am still with you.
Oh that you would slay the wicked, O God!
O men of blood, depart from me!
They speak against you with malicious intent;
your enemies take your name in vain.
Do I not hate those who hate you, O Lord?
And do I not loathe those who rise up against you?
I hate them with complete hatred;
I count them my enemies.
Search me, O God, and know my heart!
Try me and know my thoughts!
And see if there be any grievous way in me,
and lead me in the way everlasting!