Weep With Those Who Rejoice

There's a running joke that I have no idea what to do when somebody cries in my presence.
I instantaneously cinch in my shoulders and awkwardly pat backs and mutter encouragements. However, I do feel for them. I hurt for them and sometimes, unknowingly I carry it for them.
Weep with those who weep. 
I get that scripture, even if not in a literal sense.
When someone hurts, hurt for them. Feel that pain inside and help them bear it to the Lord.
Rejoice for those who rejoice. 
I don't get that scripture, literally or figuratively.
OK, I get it, but I don't always like it.
This goes way beyond buying baby gifts or "liking" engagement pictures. To rejoice is to experience joy. It's to celebrate. When you rejoice, you feel joy deep inside of you and it fleshes itself out in action.
Rejoice with those who rejoice means to feel that deep-rooted joy for others, even when you are not rejoicing yourself.
This means that when you struggle to get up in the morning and go to a job that you cannot stand, you rejoice with your brother or sister who adores the job with which he or she has been blessed.
This means that when you have waited and waited for your soulmate to make his debut, you rejoice for your sister who has found him.
This means when your friend loses 20 pounds and looks like a rock star, you rejoice!
This means that no matter my selfish desires and wants and false needs, I REJOICE WITH THOSE WHO REJOICE! 
Why oh why is it so much easier for us to weep with those who weep, rather than to rejoice with those who rejoice? 
As my sweet Leslie wisely stated tonight as we sat on my couch and discussed this with a glass of red wine, "it's because we are a sinful people".
We are ever dissatisfied with the present. If only this dissatisfaction was due to the sojourning status of our souls, but unfortunately I cannot say that is always true for me.
I have so much stake in the finite of this world, so much so that I deny joy for those who are rejoicing. Instead of celebrating the sweet, I weep for the fictitious holes that I create.
May we grow, may I grow in my satisfaction in Christ, that I would no longer need feel the need to rebuke the rejoicing of others.  May I grow to be the caliber of woman who can deeply and genuinely rejoice.