Economic Analysis

I don't like the idea of dividing the study of economics into microeconomics and macroeconomics. For me, what matters are:-

1) what are the "all other things remaining the same" in models on which economists keep drudging; and

2) the reasons behind the assumptions

It is not a "crime" to hold quantity supplied constant or to have prices remain unchanged, but it is a "crime" to "assume" such for pure analytical purpose(s) / convenience.