First of all, I am not the greatest at this. I have been taking each day as it comes. Then making my gratitude notes at night helps me sleep happier. I think about love. I think about the miniscule moments in the day. Then remind myself by writing it down.
When ever I have a negative thought I try and make sure i challenge it and really use distraction to get off that thought
I'm not sure if this can help you but… from my experience working with my homeworks, it was very difficult because I was always frustrated and depressed because I never found a technique to do it like my way, my mental concentration decreased a lot, however, I realized that sometimes you don't have to think about things that much, one way to thank is to take advantage of the things we have so we can focus on the duties we must do, you don't have to think too much about: how to be thankful or how not to be negative, or how to apply all the good habits of appreciation that I learned, sometimes we just need to face the challenge, no one said it was gonna be easy, life doesn't work that way, don't worry about what will happen next, just do what you must do and that's it, I hope I have helped you: D
I mostly write about how my day was, and how the events of the day affected me, what I thought about them, how they made me feel etc.
Even writing couple of short sentences feels good, like accomplish something.