I find this prayer so beautiful and so true:
"Do not look forward to the changes and chances of this life with fear. Rather, look to them with full confidence that, as they arise, God to whom you belong will in his love enable you to profit by them. He has guided you thus far in life. Do you but hold fast to His dear hand, and He will lead you safely through all trials. Whenever you cannot stand, He will carry you lovingly in his arms.
Do not look forward to what may happen tomorrow. The same Eternal Father who takes care of you today will take care of you tomorrow, and every day of your life. Either He will shield you from suffering or He will give you unfailing strength to bear it.
Be at peace then, and put aside all useless thoughts, all vain dreads and all anxious imaginations."
- Saint Francis de Sales (1567-1622)