Sex so quickly.

I just broke up with my boyfriend of 3 years last week. I'm not one who can just move on so quickly. Infact it will prob take me forever. But I started chatting to a guy I've known for years. Just to occupy myself. As I miss me and my ex chatting all the time. But he wants to meet up. And is talking about sex etc. Which I normally can't do with a guy right away either. But alot of friends are telling me just to go for it. To help me get over my ex already. Part of me wants to be a crazy dare devil just for once and go for it! But at the same time I'm a nervous wreck and I really do just want my ex back everytime I think of doing this! Is it true that the best way to get over someone is to get under someone else?