You don't have to be grateful.
You don't have to find yourself recognizing or appreciating anything a person does for you.
No one can argue that you ought to express gratitude for the grace they give you.
It is possible to live your entire life without a single word of thanks coming out of your mouth.
So you don't have to be grateful.
But if you were...
You would immediately find out just how much baggage you carried behind you. You would come to know the reason why you fear offering words of gratitude. Your lips even at the attempt of the first word imitate the sound of a matchstick catching fire. The flame would be forever lit in your mind about the day you found grace, and you would never forgive yourself for mocking it. The monsters in your head would all realize that they were not alone, and the light they thought could never penetrate these depths have yet again forced them deeper still.
And as you direct that word of light towards the one you wish to thank, you force the darkness to surrender its hive of corridors to the one who brought you light. There is no longer a hiding spot for your loneliness, because it has found a home in someone else. Having journeyed there from the road of gratitude, loneliness rests its hat by the door.
The only one who is alone now is you, completely disrobed, full of light, and fully found. Totally unknown to being totally open, if only just for a moment, the event permanently sealed into history. Grace has been found and it will never be forgotten.
What I am trying to tell you is that you have a very good reason not to be grateful, and that I understand why you wouldn't.
What I am also trying to tell you is that you have every reason to be grateful, if your desire is to be free.