Wow, such an intriguing question.
Marriage is a life time commitment and not something someone can just decides to walk out anytime one pleases,that's how God design it.
There is no daughter that don't want his parents to be together happily, that's the greatest joy of a child and I don't think anything can compensate for that.
No matter what might be going on in your marriage,it can be resolved and that should be the priority and not leaving and as a Christian that I am ,God hates divorce and it has an effect on your children.
So if you want your daughter to be happy, think of solution to make your marriage work because divorce is never the solution.
I recommend two things: Couples counseling and mediation.
Couples counseling will help the two of you work things out and learn to communicate so that even if you go through with plans to separate, you'll be able to put your daughter's best interests at heart and treat each other with respect.
Mediation will focus on what's best for everyone involved while also attempting to be fair and impartial about the situations with which a divorcing couple with children is usually faced. Custody, visitation, child support and so on ~ all can be dealt with calmly and rationally if the couple is willing to work with each other and accept the mediator's recommendations.
Good luck to all of you.
This is not the time to lie why you have to separate. Maybe this is very strange, but chances are your partner already knows. Communicate the reasons why you split up and mention all the fights.
2. Avoid cliches
Don't say cliché words like, "we still make friends,", "it's not about you but about me,". This will not solve the problem. You tell me the truth why you have to end the engagement without being cliched.
3. Do it personally
This conversation must be done between the two of you. Deciding the engagement and telling it is one of the most traumatic conversations. Choose a safe place, both of you, and don't forget the right time
4. Be sweet
Remember, be nice whatever happens between you two. This will be very difficult. No need to bring and condemn past actions. Don't leverage the past and mistakes. The important thing is to be nice.
5. Return the engagement ring
If you decide the engagement then you must return the ring because the price is expensive. This is the consequence.
The right way to end love relationships well without hurting your heart :
1. Determine the Right Time
Revealing the broken word to a partner can be done at any time. However, you should look at and determine the right time when you want to say it. Don't end the relationship when your partner is in a lot of trouble or is running an important event. It could be that your decision further worsens the situation. Wait for the right time and tell the truth.
2. Say Directly and Honestly
If your decision is mature, say it directly to him. Try to avoid ending your love affair through short messages or phone calls, invite your partner to meet and say what you feel. Don't make a bad impression in front of your partner. If he doesn't want to meet you, act mature to respect his decision.
3. Use the right reasons
Say what you feel, don't make unreasonable reasons. Express all complaints and why you want to end the relationship with him. Be honest with feelings that are felt, so your partner can understand your position. When you feel uncomfortable or are bored, say and don't lie.
4. Explain with Good Words
When you explain the reason why you want to end a relationship, it's not uncommon for your partner to be emotional. It is natural that it is emotional but, you should not be provoked by emotions too. Try to explain using good, smooth words. Avoid saying harshly, or even blame your partner.
5. Give time
Ending a relationship is not fun. Naturally, if your partner tends to be quiet or sad, he could be surprised and not ready for your decision. Don't push yourself too hard to accept a decision, try giving himself time to calm down and think.
6. Establish friendships
Even though the relationship is over, it doesn't mean to be an enemy. It never hurts to make your ex-lover a friend or your best friend. That way, you can still establish a good relationship with him. If your partner is not ready to become a friend, you should not force it and let it flow naturally.
it is hard to not break her heart, she will be broken for days, months and even years and that can affect her whole life, so my answer to you is don't leave your marriage, do the impossible to save your home for the sake of your daughter.