I would second everything Meagan and Chrystal said.
Also for me, it's helpful to remind myself of all the times that God has already come through on his promises. I never have to look far to find examples and most of the time they're a lot more difficult situations than whatever I'm currently stressing over. If He can handle those things then I can certainly trust him to handle whatever my situation might be.
I also try to remember his promises in scripture. If I'm really struggling to do this, I'll write the verse out and tape it up somewhere I know I'll see it like the bathroom mirror or the fridge or even the dashboard in my car. If you need suggestions for scripture, I'd say Philippians is a good place to start.
Philippians 4:6-7
Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all comprehension, will guard your hearts and your minds in Christ Jesus.
I'll be praying for you.