I recently wrote this brief letter to a friend seeking advice on prayer:
First, I'd just mention that the feelings you're having- wishing for optimism, feeling confused, seeking, all that stuff, is itself a form of prayer. In Romans Paul says that when we don't know how or what to pray, the Spirit intercedes for and in and through us with groans too deep for words. I know that's sometimes how I myself have been praying for you, and now also after hearing of the Tsunamis. I don't pray words. I groan. Sometimes I have no idea what to pray, but I trust my inarticulate yearnings are the Spirit in and through me.
As for prayers that console, I believe the most powerful thing to is to repeat prayers you know. I find myself repeating The Lord's Prayer, The Apostle's Creed, and the Rosary because they are prayers I have memorized. Sometimes I recommend that people simply repeat them over and over again. Other times, it is good to take them petition by petition and pray them slowly, reflecting on each verse.
Many of the psalms are also good. If you have a Bible, read Psalm 23, 34, 121, or 51. These are good psalms to pray when in distress.
I also have recently begun writing out my own prayers for personal use. Maybe you could sit down and write a prayer for this very situation, kind of like a poem, and then pray it regularly.
I think it's a good idea, if you are willing, to actually pray out loud. When I'm in hospital with people who are sick, I pray for them out loud, naming the things I've heard them talk about that are their prayer concerns. We conclude by praying the Lord's Prayer out loud together.
I'm setting myself the assignment of writing a prayer specifically for your situation. In the meantime, trust that the God who created heaven and earth, and called all things into being through the Word, his Son, is also the one who holds you and keeps you in all things, even in sickness, and holds all of us, through baptism and his Word, even through death. You are in battle against this thing, it is not what God wishes for you, and it is my prayer that you will be strengthened in faith to fight it in good faith. You didn't cause it. And Christ will see you through it.