What are you thankful for?

[Rayaan]

I don't see an important difference between being thankful and feeling glad.

Yeah, the words "thankful" and "glad" (and other related words) don't have much of a difference between them. They can be used in almost the same context.

For some reason, though, I get the feeling that being thankful has something extra that the other one doesn't have.

I think that thankfulness includes two things at once ... and those are ... being happy and being appreciative. This also suggests that the thankfulness may result from feeling an appreciation for some of the favors that someone has given to you (or bestowed upon you). Therefore, in that light, when someone says that he or she is thankful for so-and-so, it sounds to me as if they are expressing both contentment and appreciation at the same time, for whatever thing that they feel thankful for. That's why I think that being thankful is a little bit greater than simply feeling happy, lucky, or fortunate. It comes from a deeper place in our hearts and has more power to influence how much we value our lives.