There are many faces of grief...denial, anger, bargaining, depression and acceptance. Sometimes people get stuck in one and do not move through to the other side.

Denial can suggest to you that she will be coming back -- so you never completely grieve or move through the fact that your marriage has ended. That places a hold on you getting on with your life as a single person and parent. Anger is actually a healthy emotion -- it is appropriate and normal in divorce.
 
In dealing with anger -- acknowledge and accept the feelings, while avoiding self-inflicting behaviors and those can hurt your children as well.

Bargaining, the next phase in letting go and moving through, is sometimes a desperate maneuvering to have things "be okay again"; this seems to be the most painful of the phases because it is a tricky one. Like denial, bargaining comes in waves. Sometimes it looks like begging or even sophisticated negotiating, where people try anything to create an atmosphere similar to when the marriage "was working".

Next can come depression, which is a state, in which you feel your life has ended. You are bombarded with negative thoughts and painful projections. Depression is seen as a different flavor of anger; it is anger you have turned inward, toward yourself. Here, it is best to acknowledge those feelings without acting them out in harmful ways. Speak to a friend or counselor when faced with depressing feelings and thoughts.

Once you've placed one foot in front of the other and moved through these phases into that of acceptance -- you may be taking some deep breaths and begin to feel strong and more whole. It's like you've walked through a tunnel and are beginning to see some light -- a rainbow. It is only now, after acceptance has kicked in, that you can see clearly and make a healthy decision about your life choices.

Once you have yourself back you can then choose whether or not you want your former spouse back in your life. Don't come back to an unhealthy relationship for your children (to get back together for you're the sake of your children is the wrong motivation). If you are to return to your relationship, do so after the two of you have worked out the resentments, anger and distrust created in its wake.
 
And don’t start another relationship until you have gone through some healing and self reflection, nothing is worse for you or your children than having revolving door relationships or rebounding from one to another.You will ALWAYS be the parents of your children whether you are together or live separate lives.

Divorce and separation bring on a lot of fears and insecurities, so be sure whatever motivates you to return to a relationship with painful memories are healthy choices. Talk to a therapist if you feel you need an objective viewpoint, and take baby steps.  Be true to yourself first, and the rest will follow.