It is common knowledge to every schoolboy
   and even every Bachelor of Arts,
That all sin is divided into two parts.
One kind of sin is called a sin of commission, and that is very important,
And it is what you are doing when you are doing something you ortant,
And the other kind of sin is just the opposite and is called a sin of omission
 and is equally bad in the eyes of all right-thinking people, from Billy Sunday to Buddha,
And it consists of not having done something you shudda.

I might as well give you my opinion of these two kinds of sin
  as long as, in a way, against each other we are pitting them.
And that is, don't bother your head about sins of commission
  because however sinful, they must at least be fun or else you
  wouldn't be committing them.

It is the sin of omission, the second kind of sin,
That lays eggs under your skin.
The way you get really painfully bitten
Is by the insurance you haven't taken out, and the checks you haven't added up the stubs of, and the appointments you haven't kept and the bills you haven't paid and the letters you haven't written.
Also, about sins of omission there is one particularly painful  lack of beauty,
Namely, it isn't as though it had been a riotous red letter day
 or night every time you neglected to do your duty;
You didn't get a wicked forbidden thrill
Every time you let a policy lapse or forgot to pay a bill;
You didn't slap the lads in the tavern on the back and loudly cry Whee,
Let's all fail to write just one more letter before we go home,
 and this round of unwritten letters is on me.
No, you never get any fun
Out of the things you haven't done
But they are the things that I do no; like to be amid,
Because the suitable things you didn't do give you a lot more
 trouble than the unsuitable things you did.
The moral is that it is probably better not to sin at all, but if
 some kind of sin you must be pursuing
Well, remember to do it by doing rather than by not doing.