Penis size is very important to a lot of woman but so are a lot of other things. You just have to have what turns them on I suppose.
The author of that web site has some problems and that observation comes from a guy who is always called big. It seems designed to make most men feel inadequate but then our system seems designed that way at times.
Don't kid yourself though. If you just shrunk from cold water or a bad day.....don't even let her know. It might be Cya. Women are much colder than men in that regard. Very, very few men will say cya because a girl has average sized breasts if she has other attributes.