Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 1
The depression came into you subconsciously because you had the discussion with X. When you discuss like that with people, 
you put something in them, but something also comes from them to you. So, as X was not in quite a good condition, though nothing like what he used to be in his depressions, you easily got a touch of it and as soon as the subconscious could find a habitual excuse it sent it up to the mind. You should always be on your guard against these automatic interchanges. A little care is sufficient – and no needless discussion.