Friend who is the same in happiness and sorrow

[Sigalovada Sutta: The Discourse to Sigala The Layperson's Code of Discipline](http://www.accesstoinsight.org/tipitaka/dn/dn.31.0.nara.html) includes, > "These four, young householder, should be understood as warm-hearted friends: > > (1) he who is a helpmate, **(2) he who is the same in happiness and sorrow,** (3) he who gives good counsel, (4) he who sympathises. And > (2) "In four ways, young householder, should one who is the same in happiness and sorrow be understood as a warm-hearted friend: > > (i) he reveals his secrets, (ii) he conceals one's own secrets, (iii) in misfortune he does not forsake one, (iv) his life even he sacrifices for one's sake. I thought I could guess the correlation between being "warm-hearted" and being "the same in happiness and sorrow"; but, my guesses didn't really match any of the four ways given, except for the 3rd way (i.e. perhaps I understand why "being the same" includes "does not forsake", but don't understand the others). So: - Does "being the same in happiness and sorrow" mean [Upekkha](http://en.wikipedia.org/wiki/Upekkha) ? - Does "warm-hearted friend" mean [Kalyana Mittas](http://en.wikipedia.org/wiki/Kaly%C4%81%E1%B9%87a-mittat%C4%81) ? - Why are revealing and concealing secrets mentioned? What kinds of secrets? What do "secrets" have to do with being "the same in happiness and sorrow"? - The last item, "his life even he sacrifices for one's sake" -- can that be reconciled with the answers to the question, [How to be compassionate to a friend in need](https://buddhism.stackexchange.com/q/4053/254) ? Those answers seem to suggest that you can only help yourself.