What I’ve come to like about this place is that when I find a great question like this one, I am almost certain to find excellent answers and posts to it, as opposed to just crap, one-liner pseudo-intellectual crap or just banter between friends.
This question makes you think, and the 20 or so people above me either tried to answer it intelligently, intellectually or personally. This is great, imho.
You asked: Where is the line between personal responsibility and the impact of others on our lives? Is it all in our reaction to life/people, or do life/people create our problems?
Life, as the great John Lennon wrote, is what happens to you while you’re busy making other plans. Once you understand this, everything makes sense and you begin to “blame” others less, blame yourself less, and in general, just swim a little more efficiently in the sea of life.