Original goal to retire at 55. Retired in 2013 at 58. No regrets and in hindsight could have gone out at 52. My indicators of "enough":
1). I occasionally buy a lottery ticket. I never think to check to see if I won until I stumble across the tickets weeks later when clearing off my dresser. Winning the lottery would not change our lives other than perhaps adding the hassle of fending off scammers.
2). When hiring someone to do work on my house, RV or yard I worry about them doing quality work, not the cost. I'll always take the higher bid, if there is evidence the work will be better quality and on time.
3). Our investments are sufficient to to replace my pension income should the megacorp paying it go under.
4). I elected to draw SS at age 70 because we don't need the income today.
5). I made a very detailed 25 year budget projection when I retired. Even with far higher medical costs than anticipated, we spend less annually than the total annual spend of the benchmark budget. In retirement we spend less than 40% of what our salaries when working supported. Of course in our working years we lived far below our means in order to save, so it was easy to continue.
6). If today someone offered me a job paying several times my highest income working year, I would not consider it for a second. Being able to choose what I do with my time everyday is priceless.
7). Net worth continues to grow in retirement on a conservative 40% stocks, 60% bonds portfolio.
8). We are shedding "things", not accumulating.
9). The experiences which give us the most pleasure, have a negligible financial cost. An evening sitting by a campfire at a state park with our RV camping friends has infinitely more value to us than a luxury river cruise in Europe.
10). We wake up in the morning, and go to bed at night, smiling. After all, every day is Saturday.