When you are on a spiritual path, you are not thankful or obliged to anybody. In the Gita, Krishna says, "He is dear to Me who neither goes on thanking people nor hates anyone (Na abhinandati na dveshthi)." Thanking and feeling obliged indicates that you believe in some one else's existence rather than in the Divine who is ruling everything. When you feel obliged, then you are not honoring the principles of karma or the divine plan.
Appreciate people for what they are, do not thank them for what they do. Otherwise your thankfulness is centered around ego. You are grateful, but not for an act. You are grateful for what is. As every individual is nothing but a puppet of the ONE, thanking and being obliged is simply an exhibition of ignorance. Everything is ruled, controlled and managed by one Divinity, that consciousness has to shine forth in every act of yours; you do not have to make a mood of it.
Q: Guruji, we are so grateful to you, what should we do?
Gurudev: When you have a total sense of belonging, then gratefulness does not become an obligation. Such gratefulness is for the Divine only, which enhances strength.