In my words, be grateful for a thing, no matter how small or big, we should appreciate it and make the best use of it.
When somebody is in very need of something, we can help that person in need, it would be a very big thing for the person and can even change a person's life. The person may remember the thing done for him or her. The person will be thankful as well as grateful for the help.
But being grateful for someone doesn't mean one should always bow before the person to whom the person is grateful and do everything, wrong or right, for that person who is providing the things to you.