Reading all the posts above,I can't help but to give my opinion

I agree with Qwerty and bigmac79,in a way.

The thing that gets me is that,I think one of the reasons that James is married/interested in AM, is her maturity considering her age,her confidence as a woman/actress,her invulnerable-ness(does that even a word?),things like that.AM is already in the industry when they met.She must be much more experienced than James.It's just that she's more into the plays,and not big hollywood movies.

In the other hand,James is not willing to be an actor even while Shameless is booming in the TVs.In interviews,he had said that he felt acting 'is accidentally' happening on him.And that 'I'm just using the industry,I'm not going to be an actor.If no one pick me to be in movies,it's ok' thing.He's the one with insecurities,not AM.And AM is the one who tell him to follow his thespian instincts.He mentioned this in BAFTA acceptance speech.Maybe he wouldn't be where he is now if AM never existed in his life.

From my view,James is a kind of man that needs,and AM provides it.I think that explains the age gap.Older woman is more secure,know themselves,while younger woman still with their insecurities.

I hope AM is talking about past experience.But if she really is talking about their marriage,it's just that she had her moment of weakness,suddenly feeling inadequate to James.I think that's what popularity does to married couple of actors.