Hi, I'd like to help you with your question.
It sounds like you feel you are a bad person for leaving the marriage. The nature of guilt is to cause us to feel bad when we do something wrong. So by feeling guilty, you are telling yourself that you are wrong for leaving the marriage. However, from what you said, you were miserable in the marriage and have been for a long time. Would it have been right to stay, even if you feel unhappy?
One of the questions here is what is making you feel bad and wrong about leaving. Is it just the marriage in general or is it because your wife has a handicap? That is an important question to ask. If you left because the marriage itself made you unhappy and you feel guilty about that, then you feel it is bad to leave a marriage at all.
If you are feeling wrong about leaving because of your wife's condition, then that would be a stronger guilt because of societies expectations of us as human beings. When someone is down or vulnerable, our society says it is wrong to turn our backs on that person. We are seen as "heartless" or without compassion. In other words, "bad" people. But the dilemma here is that you felt your marriage was over before your wife had the handicap. Your feeling bad may be that you feel others would see you as leaving your wife because of the handicap, which is far from the truth.
What you need to realize in your situation is that you are not a bad person. Guilt implies you are bad. Changing that feeling to sadness and remorse is important. It is important to realize that you would not be feeling guilty if you were a bad person. Bad people don't care about how they treat others nor do they stay in marriages to help someone when it's already over. You do. So you are not bad. By leaving, you are coping. You gave of yourself longer than most people would have. Changing your thinking about the situation will help you realize that fact.
Seek out help. Talk to a therapist about how you feel. To find one, talk to your doctor for a referral or search on line at http://therapists.psychologytoday.com/rms/. If you attend church, you can also talk with your pastor. Guilt is a common feeling in people who care and have morals, so pastors can offer solace and comfort in your decision.
There are also resources that can help you at home. Here are some to get you started:
Transcending Divorce: Ten Essential Touchstones for Finding Hope and Healing Your Heart by Alan Wolfelt
Crazy Time: Surviving Divorce and Building a New Life, Revised Edition by Abigail Trafford
You can find these on Amazon.com or your local library may have them for you.
Keep in mind, you are not abandoning your wife. You still have a connection through your children. And from the sound of your description of your relationship, she can probably still call you if needed. That relationship may always be there. But moving on is good and will help both of you to be healthier mentally and emotionally. It may even improve your relationship.
I hope this has helped you,