This piece from the Guardian lists the top 5 regrets of dying patients, as recorded over the years by an Australian palliative care nurse named Bronnie Ware. The five most-frequently heard regrets were these:
1. I wish I'd had the courage to live a life true to myself, not the life others expected of me.
2. I wish I hadn't worked so hard.
3. I wish I'd had the courage to express my feelings.
4. I wish I had stayed in touch with my friends.
5. I wish that I had let myself be happier.
Look at the article for a bit more detail, or read Bronnie Ware's book. More importantly: be true to yourself, don't work so hard, say what you're feeling, look up those old friends, and smile.