So why do we need God really?

A rather alarming title for a rather innocous piece( I can't help it, thats what I learnt from most newspapers).
Personally I have always believed in the presence of an almighty God , but then I also accept Darwin's theory. So how can I recncile these two ideas? Quite simply by acknowledging all the scientific proof in front of us points to there having been an Evolution. God on the other hand is an idea for which there is no proof, truly a matter of faith.
I have experienced highs and lows like most, and the idea that there was a God helped in the bad times by providing hope that times would improve. In good times it gave me a reason to be grounded. I have never been overtly religious since I don't believe that the idea of aGod , is dependant on any religion.
So now to come down to why I am writing this piece, a sudden realisation. The realisation that we need the comforting idea that somebody is watching over our actions(as well as those around us), so that no good act goes un-rewarded (in our case) and no bad act goes unpunished (in the case of the rest). Without that knowledge(somebody is watching) there is no incentive to do the right thing and in cases where u can get away wth it, no disincentive to do the wrong thing.
But wether u call it karma or "what goes around comes around" , nature has found its ways.