The entirety of Psalm 63 ministers to my heart. It voices my prayer, especially in the hardest of times when I am weakest. Here are the first few verses:
O God, you are my God,
earnestly I seek you;
my soul thirst for you
my body longs for you,
in a dry and weary land
where there is no water.
I have seen you in the sanctuary
and beheld your power and your glory.
Because your love is better then life,
my lips will glorify you.
I will praise you as long as I live,
and in your name I will lift up my hands.
My soul will be satisfied as with the richest of foods;
with singing lips my mouth will praise you.