"The first enemy is excitement — the tendency to think and feel about the war when we had intended to think about our work. The best defence is a recognition that in this, as in everything else, the war has not really raised up a new enemy but only aggravated an old one. There are always plenty of rivals to our work. We are always falling in love or quarrelling, looking for jobs or fearing to lose them, getting ill and recovering, following public affairs. If we let ourselves, we shall always be waiting for some distraction or other to end before we can really get down to our work.The only people who achieve much are those who want knowledge so badly that they seek it while the conditions are still unfavourable. Favourable conditions never come. There are, of course, moments when the pressure of the excitement is so great that only superhuman self-control could resist it. They come both in war and peace. We must do the best we can."