A long time ago, I heard this from a sales training record, that there are only three jobs in life:
1. Filling the things that are empty.
2. Emptying the things that are full.
3. Scratching where it itches.
I've often thought of this since the early 1970s when I first heard it and I think I have to agree that every job I can think of falls into one or more of these three categories.
Just a bit of trivia for your enjoyment!