Having been branded as Mr Grumpy by my children (that I choose to take as code for 'Dad won't let me have my own way') I've finally found the justification for my Meldrew gene, which, rather neatly, I can now put to good use while marking:
"An Australian psychology expert who has been studying emotions has found being grumpy makes us think more clearly.
In contrast to those annoying happy types, miserable people are better at decision-making and less gullible, his experiments showed.
While cheerfulness fosters creativity, gloominess breeds attentiveness and careful thinking, Professor Joe Forgas told Australian Science Magazine"
Only mark when you're grumpy - Official
I knew it all along!