In the morning because at the start of the day i have clear mind so if i think about what am i grateful my day will be better and happier
I personally like to do it at night, because it helps me realise that even if I’ve had a bad day, there were still things to be grateful for. It also gives me peace of mind when I’m going to sleep.
Why not both. Use the morning to state what all you are grateful for that is sort of permanent like a family member or an opportunity that changed your life. Use the night possibly before bed to state what all you were grateful for that day like someone doing a good deed for you or something that made you smile or ponder upon it. That’s my advice but acknowledge what you are grateful for however you like and whenever you like. Fine tune the action to you as well as any other habit you might want to form.