“If you say that an idea or action goes against the grain, you mean that it is very difficult for you to accept it or do it, because it conflicts with your previous ideas, beliefs, or principles.”

In other words, going ‘against the grain’ – if you do it sensibly, of course, is a better survival strategy than ‘going with the flow’.

Simply because going against the grain will prod you to discover a solution for the next challenge while going with the flow will hone your expertise in solving the last problem you have encountered.