How do I keep positive?

Ok, here's what happen. My best friend of 9+ years told me that she is in love with my ex who is also a friend (my friend has a track record of falling for her friends' current or ex girl/boyfriends). And she said that they have been lying to me for about a month cuz they didnt want to hurt me, I guess. Thats not a reason to lie. A few weeks before the news was broken to me, I had sensed something was going on and I even gave the both of them a chance to fess up. And both looked me straight in the eyes and said that there wasnt anything. So I believed them. I think I am more upset that I was lied to. I dont like to be lied to. Where I come from, trust, loyalty and respect are a big part in having any kind of relationship. Personally, I believe that any current or ex girl/boyfriend of your best friend is off limits if you plan on keeping a relationship with your friend if not, then its fair game. In my case, I get the feeling that they wanted to get together and still be besties with me. I don't think so. With that said, I severed ties with the both of them. My ex, seems to be more remorseful than my best friend though. Yes, I am hurt and I am trying to be positive. How do I do that??How do I keep positive?
meet new guys and hang out with friends who dont care if you complain about life. and keep in mind that unless you have told a friend that u plan on going back out w ur ex, he is actually available. she can go for it if she wants bcuz ur not with him anymore. but no it was not right 4 them 2 lie. but time heals all. and if u want 2 keep ur mind off of it, take up an interesting hobby. my suggestions: yoga, reading, and blocking it all out w loud music. good luck.