Think the guy you mean was Tim Norfolk, who produced some brilliant lyrics in the '70s. I don't remember hearing this particular one, but recall a brilliant one called 'The Caterpillar and the Butterfly'

Included:-

When you are a caterpillar all you eat is bitter leaves,
But when you are a butterfly, then socially. you're in!

And ended :-

Here's the moral, never stop,
Crawling 'til you reach the top!

FC