Past Yet Brothering

Recently I happen to know of something, which makes me think very lowly of this guy personality. I ask myself a few questions:

1) How can a guy said he feel lose when he is about to start a new life with his girlfriend. (Shouldn’t he feel great and looking forward to his married life?)

2) How can he propose to his girlfriend while on the other hand tell his ex how he miss their past?

I really feel this kind of guy is horrible... :( Yet in the past, I use to innocently think that he is an introvert that's why have a lot of issues not shared. Now I feel that it is not due to his introvert character, it is more like he has many things that he dare not expose in daylight.