So much of what we describe as 'understanding' is in fact 'overstanding' - in the sense that we think that knowing the causes of drinking, infidelity etc will magically mean we have some control over them. Sure, sometimes it can be helpful to realise that someone's behaviour is a common consequence of their alcoholism - if we can then let it go.
For me, 'understanding' has included the realisation that the person I'd been in love with doesn't exist - he was a fantasy drawn by the man himself and then fleshed out by my own vivid imagination; that people who are deliberately obscure and won't give straight answers aren't clever - just poor communicators; that people who are permanently critical aren't perceptive - just critical... I could go on...
For me, 'understanding' has been that life is very, very much simpler than my alcoholic family had brought me up to believe and, as desypete says - it leaves freedom in the mind.
I'm loving this thread!