I've been getting a lot of email these days from folks that are planning to retire in the next few years. They share a common theme, excitement tinged with fear. Even though they really do want to retire, they wonder whether they have really figured the money part right. They are a little nervous. There's a word for that, it's called normal.
As Ram points out in his recent post "How Irreversible is the Decision Really?" it doesn't have to be that scary. For one thing, it's not really an all-or-nothing decision, "people who have only worked full-time don't seem to fully appreciate the range of options that are available. Options like taking up part-time work or consulting or freelancing."
Don't worry so much about the precision of your calculations, instead figure out how you will respond if circumstances require you to make adjustments along the way. A few tips for getting more comfortable with your decision are in my post at U.S. News today, "5 Ways to Tell if You Are Ready to Retire."
This is a post from Retirement: A Full-Time Job