Philippians 4:6-7.

These two verses have always encouraged me to not be anxious, but to give all my worries to God and allow His peace to replace my fear. But being in all my Bible classes has taught me to look at the whole context of passages... so here is Philippians 4:4-8
"4-Rejoice in the Lord always. I will say it again: Rejoice!
5-Let your gentleness be evident toward all. The Lord is near.
6-Do not be anxious about anything, but in everything, by prayer and petition, with thanksgiving, present your requests to God.
7-And the peace of God, which transcends all understanding, will guard your hearts and your minds in Christ Jesus.
8-Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable- if anything is excellent or praiseworthy- think about such things."

How do all these verses tie into the same theme? Well, as believers, we can have joy. This doesn't mean we're all smiles all the time, but we have certainty that God is with us. Therefore, we can rejoice, because whatever happens here really doesn't matter in the end. Our happy moments will be so much greater in heaven, and our sad times will be no more. Rejoice! The Lord is near! He is here right now, and he is coming back one day to save us forever! Don't be anxious. Tell Him when you feel upset, and he can replace it with peace. This peace is greater than we can ever understand. It gives us reason to rejoice! In the mean time, don't dwell on thinking about sad things. To truly experience peace, fix your mind on things that are good.

(You know what else is great about the context of these verses? Check out verses 12-13: "I know what it is to be in need, and I know what it is to have plenty. I have learned the secret of being content in any and every situation, whether well fed or hungry, whether living in plenty or in want..." and I don't think I need to remind you of Philippians 4:13... It's not about being successful in everything. It's about getting through because God is with you.)