Controlling your high is about awareness of your body. How it reacts to substances and emotions, and how to learn to ignore some of those reactions when you're around others. It takes practice and focus. Mostly focus, a hyper-awareness of yourself.
Fear is controlled by allowing your body to work through it. Knowing that whatever you may be thinking or feeling is only momentary in your life. Fear is only an emotion, don't try to hide from it, acknowledge it, use it. Realize that it is a biologically useful reaction, and focus it for your own purposes.
Tolerance has nothing to do with it. When I get high I feel normal because it makes me a better person. I don't care about little things, I see other perspectives, I care about people that I don't give a shit about when sober, I learn new things and have fun doing it, I do weight-lifting and it gives me a great mind/body connection, I further my career and myself as a person. Sometimes it might make me physically want to sit on the couch, but mentally it makes me want to organize, plan, make things, accomplish stuff. When I'm sober I'm happy enough, but just not interested in doing anything that important or hard. And I hate most people. Might make me mental, but that's ok, I'm on medication.
I don't know why, but I believe some people are better off smoking, and some aren't. I have friends and know people that smoke and they just do nothing. Have no desire to do anything useful and it doesn't seem to make them better people. Makes them worse in some situations. Not that it's the weeds fault really, just who smokes it, and why.