As much as it royally sucks to have some one we care about betray us, think of it this way, without these terrible experiences we (as part of the human race) would never be able to experience happiness. Experiences exist in relation to each other.
To clarify chocolate cake wouldn't taste so damn good if you hadn't had to shovel down lima beans at some point.
Wallowing in disappointment for some time is normal, but you do need to move on. View this experience as something that will make you appreciate the good times more. Use it as a chance to grow, look at what went wrong. If you are falling for the wrong type of person, think about what you can do to avoid this situation again.
Personally, I found I was attracted to the wrong type of guy, I found I have no desire to remake those types of mistakes. I had to sit and make the effort to find the common ground with all the negative experiences. I wrote down everything that I hated about those relationships (the guys would borrow money, consistently disrespect me in being late, they lacked ambition). Now that I am aware of these things, I know what I need to avoid and the signs that will show that a person is unreliable. I can now avoid this like the plague.
Instead of being so upset think about what happened and why and do everything you can to avoid that type of person in the future.
Much love and best of luck.