Hey Yeoman I'm really sorry for you, and I think I felt a piece of what you are experiencing, but your current problem may be even greater than my own.
I agree with everyone who is saying you should not make it look like you have moved on if you haven't moved on.
The first thing you need to figure out: do you want her back?
If you do, all you can do is set about getting her back. The best way I know of that this works goes something like this:
Try your best to pick yourself up off the floor and take care of yourself. And man, take it from me, this will be one of the damned hardest things you will ever do. This is a test of your strength, give it your all to rise to the challenge. Do things that inspire you, make you feel good, and animate you. Don't dwell on your misery or what might have been, and look forward. Make yourself better starting today, and even if you acknowledge your goal is to get your ex back - don't meditate on that.
I'm not telling you to cover up your emotions, but I am telling you not to pursue them down to their darkest depths. Not only is it going to hurt your chances, it can quite honestly be unhealthy and dangerous. What I mean by this: you may be relatively normal for a few hours, doing something else like cooking a meal or whatever, your mind mostly off the problem. Then it bubbles back up in your mind, as it often will. The choice you have here is whether you want to continue to dwell on it and make yourself sadder and sadder, madder and madder, more and more desperate. Saying no to this is the narrow, crooked path. Giving in is the easy road, broad and straight. But you are capable of avoiding the misery, to a large extent.
Doing little things like working out (which chemically boosts self esteem) or doing a little travelling (maybe even just a few days in a different setting) can help a lot.
Above all, this is what you want to be in front of your ex, and you need to take the attitude that she is always watching: you are confident, you are self-sufficient, and you can go on without her (NOTE this does not mean fuck other people or play jealousy games with her, do not involve other women or men).
People want what they can't have. So if you call her everyday and beg her to come back, you're hurting yourself.
How often do you see her? If you see her a lot, tell her the next to you speak: "I need some space right now I think it's better if we're not in contact." And then stick to it - forget about her as best you can. She will eventually contact you, and if you are confident and composed in these interactions, you will begin to win her back.
I should mention that the above advice assumes two things:
A) your daughter does not cause you to see her by necessity that much (i'm not sure what arrangement you have)
B) that she left you because of some variation of "i dont love you anymore", if it is something like you cheated or abused her or a dispute over money etc, then that is another animal. but if the problem is emotional, i.e., that she does not feel "right" about you in the way she thinks she ought, then the above will help.
The longer you had been together before, the better your chances of getting her back. 6 years is a long time, so fret not.
I hope this is a help to you.
"You are not alone. Just remember to respect yourself, evolve yourself, and that you are the only person responsible for your decisions." I quote this for truth. I also want to say, I know what you mean about "not feeling like a man right now." But you don't need to be ashamed. Remember who you are, remember what you are good at, and remember you are a good person that this woman fell in love with and had a daughter with.
Good luck.