I think a bit of both... I did get to experience things in life I'm grateful for, and my life was on a fairly good path. I hope to hold onto gratitude for these things and have peace, but it can be a double edged sword if I'm not careful. The bitterness can definitely creep in ... "it's not fair, I want more good times, I want my life to continue on the path it was on etc. etc."
By the way, try not to beat yourself over taking things for granted. I relate a lot to what you said about not knowing I was happy until it ended... there's so many simple things I wish I could have back. It's actually these tiny simple things I miss the most... e.g. just waking up in the morning, seeing the sun creep through the window and feeling a sense of contentment and intrigue for the day ahead. But it's human nature to take things for granted - we simply don't know what we have until it's gone, because it's just our 'normal'. I'm trying not to let myself ruminate too much about this or blame myself etc. - I never knew what turns my life would take, of course I didn't revel in gratitude for every little small thing in life - who does?