I think the important distinction is that he is at home in the regular environment. If you are away from home without the family, everything is different; while at home only the absence is different. This absence feels massive because of the magnitude of habits formed participating in a family unit.

Ahh, that's a very good point.

When I was away from my family, I was in a different environment( new job) so to me everything was new and exciting.

For him, he's still at home nothing's changed, so he has a much clearer frame of reference to remind him of his family.

Also note that he said "The truth is that I don’t cry because I miss them, I cry because I never fully appreciated ....." . He doesn't cry because he misses them. It is true with me as well and probably other folks who are claiming they don't cry. I too don't cry just because I miss them, but there are moments when the mind wanders into deeper thoughts , like what really matters in life, the silly little arguments you may have had with your wife in past, the times you ignored your kids needs (taking them to parks, play with them by putting aside your laptop etc) etc, and realize how silly those mistakes were, and how easily they could have been prevented when you think about the bigger context/meaning for your life is that time you spend happily with family and it is not going to come back. Time lost is lost forever. It is thoughts like these that make me cry, make me modify my future behavior for better.

Btw, I go thru this cycle of "self-realization/self-correction and then when the family returns back from vacation , then slowly getting back to the lazy original attitude of taking some of the things for granted about family and then back to summer and missing the family" :-).

I just hope that each of these cycles keeps making me a little better person than before!

No-one can tell you how you should or shouldn't feel but personally, I can empathise with the author.

I'd really struggle if I was away from my wife and son for three weeks or more. If it helps with context, I'm a big, old fashioned Irish guy who's dealt with a lot of hardship over the years and it takes a lot for me to end up near the point of tears but I could see this particular circumstance bringing me very close.

You seem to be confused: the author states "The truth is that I don’t cry because I miss them [...]" and then you go "[...] never once did I feel like crying because I missed them. I did miss them, just not to the point of breaking down into tears:)"

In any case it is likely the author's relations to his family and your relations to your family are different and as such you feel differently when separated. It is also likely the circumstances are different.

I assume its metaphorical

because its impossible for men to cry?

    Are you surprised at my tears, sir?
    Strong men also cry.
    *Strong men also cry*![1]

[1] http://www.youtube.com/watch?v=wZbC6IIk7kQ

Let's not go down this road.

It ends in tears.