For those that like trivia, the original quote I believe is by Kernighan and it's about debugging code rather than writing it, which I feel makes more sense:

"Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?"

https://en.wikiquote.org/wiki/Brian_Kernighan

I sometimes optimistically believe that my cleverness will increase over time.

Yes but occasionally there's no other option. I once had to code a parser for a data format with an odd non-BNF grammar with a bunch of special cases. In order to meet the functional requirement for user-friendly error reporting when parsing invalid inputs I was forced to write really clever (in a bad way) code. Fortunately we haven't found any serious defects in it because I don't think I understand it well enough to debug it.

It is okay to write clever code if necessary. Solutions to some problems require it.

Clever code for the sake of being clever is rarely worthy it.