For me, the answer is that everything changed. Completely. The person that I was before I met Jesus is completely different from the person that I am today and the difference is so large that it's tough for me to understand how I lived that previous life for so long.
Ultimately, though, the biggest change is simply my attitude towards other people. In my old life I was almost a total loner. I intensely disliked being around other people and avoided them whenever I could. I particularly steered clear of parties and any other situations where there were big crowds because I simply was unable to mesh with a group of people who were having fun like that. Nowadays I am much more a people person; perhaps I'm not quite what you'd call a social butterfly, but I at least have a normal social life.
The second biggest change would be dealing with anger. In my old life I was an extremely angry person. I was furious for a large percentage of my waking life and when something bad happened I would spend months stewing about it and fantasizing about the sorts of revenge I would like to take. Nowadays that's mostly evaporated. I can't say that I never get angry, but it's certainly much less than what it used to be.
