This one's a bit of a "duh" for me, as I've developed an ongoing attitude of gratitude for my life. I practice thankfulness a lot simply because it feels good. There can be a temptation toward transactionalism--if I say "thank you," God will like that and bless me with what I want, i.e., I'll score points with God. While a vibration of gratitude tends to draw more to be grateful for, it's not because we've made God happy, it's just the vibrational nature of the Universe. It's energy law.
I believe we can bring to Spirit all that we are, all of our distress and all of our joy. Think of a friendship wherein you only shared one or the other. That wouldn't be a complete relationship. We can't hide anything from our higher Self anyway, so it's useless to try. Celebrating our joy and abundance feels so good, and it is a great practice to recognize even the tiniest things to appreciate. It is comforting to me to know that Spirit can handle anything that I bring to It.
Joyful, abundant, grateful,