I've read just about every blog on this site and even read Chase's book. I put into action what I learned from the blog as well as my own personal style. And guess what I was able to get girls , I wasn't relying on luck or hope. I relied on skill and my own drive. The truth is I've seen all this (cheating) on both sides of the field. "If" your girlfriend cheats on you, learn. And realize that maybe "I" wasn't a great boyfriend. Maybe "I" was being too selfish or elusive to keep the relationship going. Then better yourself. You know what though I changed to be able to be a romantic man, that my current girlfriend loves and appreciates. I don't supplicate or even spends loads of cash on her because simply I don't have that. I have the ability though to give her a great experience.
When someone cheats on you its not the end of the world, rather its the opportunity to take on the world. You can find someone better and be someone way cooler. Get your new girlfriend involve and work together like Ricardus said improve together. Do new things and most importantly love yourself before you can love others. Let the past go and simple live and enjoy your life. More importantly don't try to force a fit into a relationship. In your heart you always know that maybe this may or may not have been a good idea. But, hey I wouldn't like yoga or skateboarding if I never tried them. ;)