Seems to me the problem some have with retirement is how they approached it.  Retirement should be more than just a goal, it needs to be planned as a follow on career.  Having a plan for how to get there AND having a plan for what you're going to do when you get there is, I think, the key to having a happy, rewarding and successful retirement.
I had a retirement plan in mind and a financial plan for how to achieve it when I was unexpectedly retired two years earlier than I'd planned.  (Company cutbacks.)  But I was well ahead of my plan - had my retirement toys purchased, my debts all paid off, my plans well laid out for what I'd do when the day came.  I could have gone earlier by making the decision myself, but being a bit risk adverse I found that was a tough call to make myself, although in retrospect I should have done it!  Thankfully I got kicked out the door in a RIF that offered some unexpected financial rewards.  For the first six months I was a bit anxious wondering if my plans were solid, but it turned out that worry was all for naught.  The best thing that ever happened to me was getting RIF'd!  And I find I'm busier now than when I was working.