After years working in palliative care, Bronnie Ware wrote a book about the most common regrets that the people she had cared for had expressed to her (see below for a posting of her Ted Talk).
Regret 1: I wish I'd had the courage to live a life true to myself, not the life others expected of me.
Regret 2: I wish I hadn't worked so hard.
Regret 3: I wish I'd had the courage to express my feelings.
Regret 4: I wish I had stayed in touch with my friends.
Regret 5: I wish I had let myself be happier.
"The Top Five Regrets of the Dying: A Life Transformed by the Dearly Departing" by Bronnie Ware.