New Hampshire courts recognize that divorcing spouses know what's best for their child. Consequently, they encourage divorcing spouses to agree on child custody and child support voluntarily, without court involvement. If divorcing spouses agree on these issues, the court is very likely to approve the agreements. It follows that the most important thing you can do to minimize the emotional pain, impact on the child, and expense, of your divorce or civil dissolution is for you and your spouse to resolve as many child support and child custody issues as you can.
"Everything ends badly, otherwise it would never end."
Like most things in life, that's easier said than done. You are angry. You are sad. You feel betrayed. It's all [insert your partner's name here] fault. He/she is a cheater. The emotions are valid, but the predictable result is that you want to punish or "get back" at your spouse, and you see the divorce or civil dissolution process as a prime opportunity to do so. You also want to keep "your" child away from "that monster."
However, you should recognize that there are three important consequences to proceeding in this fashion. First, it is expensive. You will have to pay a lawyer to prove the validiity of every issue you raise. Second, the divorce or civil dissolution takes longer. There are more hearings, more court involvement, and more rehashing of painful events. Third, the child's emotional health may be harmed. Whether you like it or not, study after study has confirmed that children need a meaningful relationship with both parents in their formative years in order to be emotionally healthy and productive adults.
Which brings us back to child custody and child support agreements. Do yourself a favor. Address the emotions you are feeling by talking to someone: a therapist; a priest/rabbi/minister; a loved-one. Don't let these emotions rob you of the ability to determine what's best for your child through agreements with your spouse. The agreements will be imperfect, but far better than any solution imposed by a court after painful, costly and lengthy litigation.