You Could Be Happy

"Do the things that you always wanted to
Without me there to hold you back, don't think, just do"
- "You Could Be Happy"
Snow Patrol

Everyone has uttered the line before, usually in reference to an ex - "I just want him/her to be happy." While this statement isn't by any means a lie, it usually is conditional. Yes, you want this person to be happy, but under what circumstances are you okay with it?
Are you okay with your ex being happy, because he is with another girl? If the breakup was amicable, it is common sense to want to see your ex find someone else who can make him happy. The condition being - is this person right for him? In other words, he may be happier because of her...which is what you wanted...but on the other hand, you don't think (from an outsider's perspective, of course) that's she's right for him, either. Yet, just the same, you're not right for him, either. And he's not right for you.
When you're functioning as a couple, you make attempts (often in vain) to influence each other's decisions. After all, you are planning a future together. After the relationship ends, decisions about how to lead your life are suddenly just that - your own. You had a certain idea about how he should lead his life to make himself (as well as you as a couple) successful. Once the relationship is over, you are both free to pursue your lives as you please, with no suggestion from the other person.
If you don't agree with the choices a person is making (that are seemingly making him happy), do you still want him to "be happy"?
The positive side comes from making your own decisions without influence. People need to be free to make their own choices, free of persuasion, no matter what the consequence.
Happiness needs to be something we can truly want for someone, free of strings, no matter how hard this can be to accomplish.