Every woman needs one of these at least once in their lifetime, why not now? So get someone to take the kids for a few hours, (unless you don't have any) and take some time for a day of relaxation!

[edit] Steps

Rent a great chick-flick, drama, or anything that you enjoy.
Grab a pair of sweatpants, and a t-shirt, and put them in your bathroom.
Collect any CDs that you might have, that are relaxing or soothing.
Start filling up your bath tub, and if you have any, and add some lightly scented bubble bath.
Before you get in, bring CD player in, and put in a CD of your choice (one of the ones that you collected).
Stay in the bathtub for as long as you need.
Upon getting out, change into the sweatpants and t-shirt, so you can be comfy.
Switch on your TV and pop in your movie of choice. While the previews are playing, pop some popcorn, or gather some snacks.
Gather up any nail-polish supplies you have, and start the movie. While watching it, paint your nails and/or toenails, and have a good cry, laugh, or gawk in suspense.
After the movie, change into a pair of pajamas, and read a good book for as long as you'd like.
After you've read, go to sleep, or, take a nice nap

[edit] Tips

Don't feel like renting a movie? Check to see if any good movies are on TV, or watch a favorite movie that you own!
You can replace these clothes items with anything you want,as long as it's comfortable. Pajamas work fine too, if you're doing this later in the day.
If you have a CD player near your bathroom, put the CD in there, and turn it up so you can hear it. This may be safer than actually having it in your bathroom.
If you don't have bubble bath, shower/bath gel or bar soap work great too.
Snack types can vary, so if you prefer veggies and dip, over chips and popcorn, go for it! This is your day, after all!
If you want, invite a few friends over for watching the movie, so you can have fun together.
Try doing this on the weekend (Saturday or Sunday), or in the evening.
If you don't like to read talk on the phone or take a calming walk!
This guide was intended for women, because men may not find it very relaxing to watch a chick-flick (boring yes, relaxing, no) or use bubble bath. But, if you're a man and find these things relaxing, these steps will probably work for you, too.

[edit] Alternatives

Meditation: Try meditating, or resting quietly with the goal of completely clearing your mind. You will inevitably start to think about something, just notice that, acknowledge it, and gently bring yourself back to a silent mind. Whatever you were thinking of will still be there when you leave this state, but putting it down for a moment, 5 minutes, or an hour, will re-energize your mind and help you to deal with any task.
Yoga: Some simple stretching of the body can do wonders to relax muscle tension as well as mental tension.

[edit] Warnings

As the tag on most CD players imply, it is not safe to operate the CD player while your hands are wet. Do not attempt.
Read the bottles on all products you are going to use before you use them, as you could be allergic to the ingredients.