The practice of gratitude is an essential practice for everyone.
The practice is not always easy. Sometimes because of events or circumstances, it is hard to be grateful.
One thing that helps me is to allow myself to vent, to get my grievances, or my bitterness, out before I do my gratitude. I give myself five minutes to release those feelings rather than hold them in.
This clears those feelings out which then leaves me open to being grateful.