There is good advice on this forum to sift through. People are correct about staying busy and improving yourself. But the things that need improving aren't always new clothes or hairstyle. If I want to save my marriage, I have to change myself on the inside. I have to change the things about me that drove her away in the first place. LISTEN to her. She will tell you what's wrong if you listen.
I am now taking my advice from God. The situation has deteriorated greatly, more for her than me. I am being patient and hoping that God doesn't want my marriage to fail any more than I do. He can't change her heart but he can work with me.
I suggest keeping Corinthians 13: 4-7 close at hand, and pray for God to help you exhibit each of those qualities of love. Always remember the first one: Patience! It is the only thing keeping me from going crazy, or filling the void of emptiness with another relationship that would just complicate things.
Not sure for you if there has been tragedy that brought your situation on like mine, but if so: For her, I am studying the Book of Job. The basic message there is that God shouldn't be blamed for all difficulties in one's life. Sometimes SH@T happens. What's important is that when everything falls apart, God will always be there to pick up the pieces and put you back together again.
Take advice you read on here, but prioritize God's messages before all others like I am and hopefully things will change.