To fight negative emotions we have to stop thinking over and over again about the problem. Instead, do a Google search on the best Scriptures to memorize. Find a few that speak to you and get started. God is way bigger than the problem that triggered your emotion. Let Him speak to you through scripture.
Secondly, depression is not a Godly trait. To fight depression consider praying: “Father, what do You want me to do.” Of course, you can do a bunch of the ideas listed on this site, and they will help. But… give God a chance to show you something.
Jeremiah 29:11 ESV
For I know the plans I have for you, declares the Lord, plans for welfare and not for evil, to give you a future and a hope.
Consider praying one million times: “Father, show me the plans You have for me.”
If you are obsessed with what God wants… you will be well on your way to defeating negative emotions.
Finally, if you add to this working on the habit of replacing thoughts of _____ with better thoughts, you will have just hit a grand slam home run.