Is Negativity more powerful than positivity?

Today a friend inquired about why I don’t drink, don’t smoke and don’t eat non veg. He wanted to know that why I am still missing the enjoyment he and other friends get from these things. His thoughts were that I might not have done these things early in my life because my parents had not allowed me. Now when I was living hundreds of kilometers away from them, independent, free to make any decision, why had I not started any of these enjoyments? I have been asked these types of questions often by friends. Most of the times, I am not able to satisfy them logically by my answer, because my answer includes some reference to my religion, Jainism, but they want is pure logic. It was no different this time. But after many incidents of this type, my mind was forced to find logic behind this choice of mine of not smoking, drinking or having pieces of meat and bones of a poor unlucky animal in my plate.

I had been a science student, and science says that there is logic behind everything in this world. So, logically, there has to be some logic behind this reasoning of mine. And after some logical thinking, I found that there is a reason for everything we do. We eat because we feel hungry, we earn because we can have something (veg or non-veg) to eat, and I am writing this because I want to share my thoughts with you. So perhaps there is a reason behind everything, and reason can be positive or negative. Positive reasons encourage us to do something, while negative ones make us frightened, skeptical of doing something, and sometimes force us to take a back seat. But the question here is that which one is more powerful? I find negative reasons to be more powerful in most cases. You may have lots of positive reasons for doing something, but most of the times, one negative reason is powerful enough to convince us to not to do that thing. For example, fear of failure stops us from trying something new in our life. A novice speaker has fear of crowd; students do not answer questions in class because they might get their answer wrong and others might laugh on them, juniors do not put their idea in team meetings because seniors might reject it. A batsman looses an opportunity of hitting a six because he is feared of getting caught if he plays his shot in air. And those don’t fear; end up making bowlers feared from them, like Sehwag or Chris Gayle. In Math, you multiply infinite number of positive numbers with one negative number, and the whole result is negative. In software, a program of thousands of lines of code gets spoiled by one wrong statement.

So negativity is much more powerful in most cases. That’s why great men tell us to think positive, to be optimistic.

In my case, I can think of many negative reasons, but not even a single positive reason to drink, smoke or eat non-veg, so I don’t do it. I am thinking highly negative here, but will continue to do so, irrespective of what wise men say.
Which one is more powerful in your case? What do you think?