Time
After so long, you lose your affinity, your method, your language and craft. Or so the sentiment goes. But of course we mythologise and muddy the truth of our endeavours to romanticise what is a labour, and reduce what is an art to a procedure, or an algorithm.
You come back to it, again and again, if you can see sense, purpose and vocation in it. Remembering that deep fear that if you lose one discipline, you lose all.
Don't you?