I couldn't think of any other way to put it.
Have you ever noticed how much of how we react to things, our moods, our feelings have to do with other people or our surroundings? It's like we're completely dependent on the outside for what goes on inside. You could be happy one second, and then someone would tell you something that would make your happiness melt away like the sun vanishing behind clouds, leaving you with an abrupt kind of coldness. So much that we do depends on what sort of a mood we are in, and we make so many mistakes that we regret later, just because the 'situation' we were in forced us to behave in such a manner.
I, for one, know that I have done a lot of things that I look back at an wonder if I'd been possessed, because I wouldn't do things like that. NORMALLY.
Not to get too technical, but cold-blooded animals depend on heat from outside to keep them warm, because they lack the ability to maintain a decent body temperature on their own.
Sound familiar?
But yes, there are those few who can relate to things yet not be affected by them. Those lucky few are the ones who always know what they're doing, and how they're going to go about getting what they want without getting hampered by their surroundings. Mothers call it 'getting influenced'.
But everyone in human, and getting influenced is part of being a cold-blooded mammal.