Surprising, indeed

I recently read this quote
‘If you are grateful I will give you more of My Blessings; but if you are ungrateful verily, My punishment is indeed severe.’
I believed it was an usual new age writer, but – with my surprise – I discovered that it is a quote from Quran (14:7).
I asked about it to a muslim friend, and he said to me that – in spite usual prejudice – gratitude and peace are the core of the teachings of Islam, and that we must be grateful to God, not just for what we perceive to be blessings but for all circumstances.
I was really surprised, and I think we need to know better something before to talk about it.