Hmm..

There's a really thin line between humility and wanting people to see how humble you are (which in fact is showing-off)

There's a really thin line between helping others for their own good and helping others for your own credit.

There's a really thin line between a favorite 'something' and idolatry (finding security in something more than God)

However, there are many lines that aren't so thin as well.

There's no difference between a BG relationship and two friends messaging each other mushy texts. (what we would call the usual nonsense kor-mei-daddy-ahma relationship) *unless it's done immaturely with innocence... Never really the case though.

There's no difference between a 'christian' who has not shown any change in his/her life and an atheist.

There's no difference between publishing those nonsense
'if you like me (X)'
'if you would date me (X)'
'if you hate me ( )'
on facebook
And a highly insecure person.

There's no difference between going to church for the wrong reasons and hanging out at a social club.

There's no difference between a lot of things.. Hopefully God helps us in our discernment more and more each day.