Saying I do not know is a convenient excuse.
You live, therefore you should learn- whatever age or subject matter.
This Rowenaism has been with me since I was a puppy until now that I am a full-grown biatch. I adopted it since I read this blurb about learning, which I share below (i did not write it, i wish i did).
I think it might have come from the book Excalibur as there is some old fart called Merlin who is doing the lecturing. Hope it can help you as much as it did me- it really saved my sanity from my darkest moments when instead of self-destructing, I chose to learn.
I didn't dare change anything, here goes:
"The best thing for being sad, " replied Merlin, beginning to puff and blow, "is to learn something. That is the only thing that never fails.
You may grow old and trembling in your anatomies, you may lie awake at night listening to the disorder of your veins, you may miss your only love, you may see the world around you trampled in the sewers of baser minds. There is only one thing for it then- to learn.
Learn why the world wags and what wags it.
That is the only thing which the mind can never exhaust, never alienate, never be tortured by, never fear or distrust and never dream of regretting.
Learning is the thing for you.
Look at what a lot of things there are to learn- pure science, the only purity there is. You can learn astronomy in a lifetime, natural history on three, literature in six.
And then, after you have exhausted a million lifetimes in biology and medicine and theocriticism and geography and history and economics, why, you can start making a cartwheel out of the appropriate wood and spend fifty years learning to begin to learn to beat your adversary at fencing.
After that, you can start again on mathematics until it is time to learn to plough."