Hello, advice?

Hello, okay... 
I have a boyfriend we've been on and off quite a while now. Recently we've got back together (last Monday. U.K.) 
And he's told me not to be clingy or attached...
That's a problem... I get attached to everyone I meet... 
I'm clingy and I know most people don't like that, but I want to find out has anyone got any advice on how to be less attached or clingy? Very much appreciated.