It builds up a barrier which will last for life.

I did not want that barrier to rise between Dick and me--I--" and her voice shook a little--"I should be very unhappy if it were to rise.

So I have always tried to be his friend and comrade, rather than his mother." "Yes," said Colonel Dewes, wisely nodding his head.

"I have seen you playing cricket with him." Colonel Dewes had frequently been puzzled by a peculiar change of manner in his friends.

When he made a remark which showed how clearly he understood their point of view and how closely he was in agreement with it, they had a way of becoming reticent in the very moment of expansion.
The current of sympathy was broken, and as often as not they turned the conversation altogether into a conventional and less interesting channel.
That change of manner became apparent now.