Pure opinion steeped in truth, quality action-oriented therapy, awesome friends who've also traversed this awful path with success.
  1. Talk to your spouse.
  2. Start seeing a therapist, marriage counselor, whatever, on a regular basis.
    Separately and together.
  3. Try absolutely everything within your reach, take every opportunity. Do not give up or give in. It will get harder before it gets easier, so dive in sooner than later.
  4. Talk to your spouse more. Put yourself in his/her shoes to see a different perspective that you may not be able to consider clouded by pain, regret, resentment, grief or anything really.
  5. Be honest. Brutal honestly is far better than not speaking up. Respect your spouse enough to remember they deserve the truth.
  6. Be open. Listen. Get to the heart of the matters.
  7. Do not call a lawyer until absolutely every angle has been exhausted. Or until the other person refuses to continue trying, after many efforts. Don't allow either of you to give up before you put in the hardest work of your life.