Keep it simple. Think of the things in your life that make you happy. Think of what others dont have that you do have. Live according.
Hello: Sometimes we don’t feel grateful. That’s okay; we’re human beings after all, and not perfect. The trick is to not stay that way. Personally, I make a “gratitude list” every day. It only takes 5 minutes. If you feel like trying something different, then make a list of things you take for granted. For instance, did you put two shoes on today? Did have enough to eat? Do you have clean clothes? Etc.
As ungrateful takes most things away…. It can’t ruin you being grateful for authentically feeling!! Lol
I’m prayin it goes away too!!
I make a grateful list about things we take for granted. Such as, I am able to get out of bed in the morning w/o assistance. My kidneys work. Actually, All of my organs are working. I am able to walk and move and dance w/o pain. I feel so lucky and grateful for all of it. Look for and focus on all the good stuff. It’s there, I promise.
Think positive . Think of things to be greatful for . I'm not Shure exactly what your going through . But just think there are some who are less unfortunate. Prayer and meditation helps a lot for me . I hope you find gratitude and peace in what your struggling with
All great suggestions so far!
I LOVE writing, so i always suggest writing 
Anyway...sometimes I grab a notebook and make a timeline of my journey from my "rock bottom" to where I am now...it can be an actual timeline, or the story of it, bullet points, flow chart...lol...really, whatever works for you and is quick enough to be convenient. Not only will it help you to be more grateful in the moment, but you can also pull it out later on if you feel this way again and remind yourself why you're lucky and blessed
and have a grateful heart. 
for me what always gets me grounded is that i tell myself, I am human and I will feel things. I am human and i will have bad days. I am human and I make mistakes. I usually repeat this to myself to get out of the mindset of striving for perfection. Out of the idea that everything has to be just right. Self love for me helps me to calm down and reflect on the good things in life. Sometimes getting simple and realizing that you are grateful for a bed to sleep in helps me get myself out of ungratefulness
I like to completely unplug from tech and get some sunshine to uplift my mood and regain focus and mindfulness when I feel like this. The older I get the more I need to do this.