The impact of our reactions

So I've been thinking lately about the impact our reactions have on people, especially when they're confiding something deep and painful in us. The week before Thanksgiving I shared what was happening with my friend "X". Normally our friendship is one of joking, teasing and good natured making fun of each other. But my emotions were running all over the place and before I knew it I had vomited all that was in my head up over the phone with X. X's reaction is normally to tell a tall tale of punching bunnies or something equally ridiculous to make me laugh and get my mind off of whatever is stressing me out. X started to do that a little and I kindly said that I was feeling quite on edge so could X please tread carefully. X did. X's reaction could have been to dimiss what I was going through, tell me that it wasn't a big deal. X could have laughed it off and said I was overreacting. X could have reacted a lot of different ways. But X reacted perfectly. The appropriate mix of humor, compassion and kindness.
I know that I've reacted inappropriately when people come to me with their struggles and troubles and the conversation has been the lesser because of it. Trust has decreased and often a completely seperate crop of troubles arise because of my dismissiveness.
But I've been thinking lately about how important it is to not react with your first gut instinct whether it be judgement, fear, disgust etc. How much more would people open up to each other if they knew that even if the person they were talking to didn't agree with them that they would above all else reassure them that they are loved and cherished?
I joke around a lot. I can be excessively sarcastic and it more often then not comes across the wrong way. I like my sarcasm. I think I'm hilarious. (and humble). But during interactions with someone I know "A" I realize that my sarcasm and joking comes across as judgement and condemnation to A. It's the last thing I want.
So how can this be fixed. A lot of who I am is in my ability to laugh at morbid and uncomfortable things. To me it doesn't seem like the answer should be to completely squash my entire personality to make others more comfortable. At the risk of sounding like a petulant child, that doesn't seem very fair. But I can adjust I suppose, I can soften myapproach and edit myself occasionally when I know that person can't take the joking well.
But, doesn't it make sense, that if someone is confessing to you something that you don't want to hear that it's pretty obvious to them that you might not want to hear it? If they're still confessing to you, then maybe it's so important to them that to not tell you would keep a barrier up between the two of you. So maybe when people are confessing or confiding in you something that is vulnerable about them, we could focus on what is best for the other person and not what would make us feel better, more comfortable.
It's just a thought.
We all have these secret things that when revealed make us feel so at risk of rejection that it's less painful (but painful still) to stay hidden behind then the pain of blooming in full to show people who you truly are.