Pls help me to get over this! ;-(?

I've known this guy 6 yrs back. He's real sweet and gentlemen, even if you are just a friend to him. Lately we got in touch and hang out, he became more matured over these yrs, and he really attracted me. After that hang out, i kept thinking of him, I missed him. I couldn't concentrate on work and I wanted to text him badly. But I just controlled myself, as he already had a long distance relationship. And that girl is somebody I know of, so of course I didn't want to be the third party as I know they really love each other. But that guy is uncertain of the relationship now as they had different points of view. He told me abt it and my heart sank. I don't know how to hlp him as he wanted to be alone. Im single now but I don't want to start a relationship with him though I like him a lot. I just want to maintain as friends with him but how do I control the feelings towards him? The feeling of missing someone is so unbearable.