Momi,
I've tried. Unfortunately, after the first couple phone calls and flowers, you unintentionally become a stalker. Then you basically have no chance. You can try to remain friends. If you choose this path, then you need to go on with your life - date others, get out and do things, etc. Otherwise the object of your affections will end up feeling that you're only being friends in the hopes that it will get you back in the game. At that point, you again have no chance.
Your best bet overall is to move on as much as possible. It will hurt. You may feel like you'd rather be dead. With one very intense relationship, I was so hurt by the break-up that I ended up checking myself into a psychiatric hospital for a week. It's an extreme situation, but I was able to get the support I needed to heal while I was there. It took years for me to heal, and there were several relationships ruined by the shadow of that one, but in the end, when I let go, I was able to find someone else who is a better match for me.