I've been through that and I can say is a matter of taking decisions. you have to do stuff. James 4:7.
Just praying is not the solution. we have to Resist the devil, as James says, is about pray and act.
For instance do not allow yourself be alone, listen to "sad" music even if it's christian. go out, try to help others, and pray with joy and faith, if you prays are sad and complaining, your soul is not going to give good fruit.
well these are based on my experience. I had a long battle with depression but the lord gave me the victory and He is going to do the same with you!