From Alan Jacobs’ The Narnian, a biography of C. S. Lewis:

I have already noted that [Lewis’s] education and his experience had combined to stifle his imaginative side; he seems to have been determined, at this stage of his life, to extinguish it altogether– as though (again) he would be Loki’s accomplice in the slaying of Balder.  And he fully knew that Balder was moribund at best.  Writing to Leo Baker in September 1920, he said “I am more worried by what goes on inside me: my imagination seems to have died: where there used to be pictures that were bright, at least to me, there is now nothing but trivialities and worries of the outer life– I go round and round on the same subjects which are always those I least want to think about.”  And yet it does not seem to occur to him that his imagination may have been suffering as a result of choices that he himself was making.