You and your wife have been through some hard times lately, and now the two of you are apart.
  Take heart in knowing that, no matter the reason for the separation, if you really and truly believe that the two of you belong together, than you CAN get back together.
Here are some things you need to know.
First of all, don't bug her to death.
  This is probably a hard time for the both of you, and by your constantly trying to talk to her, you may be pushing her further away.
  Step back for a while, and let nature run its course.
  Hurt takes time to overcome, but it does ease more and more every day.
During this time, go out with your friends, and take care of your own mental well being.
  It will do you no good at all to sit at home and constantly think about her.
Think about this for a moment - would YOU go back with someone who seems sad and depressed?  No, you wouldn't.
  Why?  Because human nature draws us to happy, positive people.
  It makes us move away from people that seem gloomy.
  We want to feel good, not bad.
  By keeping your own spirits up, you will not only feel better yourself, but you will better your chances of winning your ex wife back drastically.
Imagine the two of you on your first date.
  Do you remember the feelings that you had for each other?  Try your best to rekindle those feelings.
  Send her a card with a picture of something that the two of you did together that you both enjoyed.
  This will encourage positive thoughts and emotions in her mind, and will make her remember the good times that the two of you shared together.
The more you can do things like this - allowing her to remember the good times instead of the bad - will have your wife coming back to you in no time!