thankful and grateful

Grateful is the normal word for people’s reactions to kindness, favours, etc.

• I’m very grateful for all your help. (not I’m very thankful …)
• She wasn’t a bit grateful to me for repairing her car.

Thankful is used especially for feelings of relief at having avoided a danger, or at having come through an unpleasant experience.

• I’m thankful that we got home before the storm started.
• We feel very thankful that she didn’t marry him after all.
• Well, I’m thankful that’s over.