I became a vegetarian originally because it was too much trouble to cook non-vegetarian meals when half the household was vegetarian.
I stayed a vegetarian because it was supposed to be healthier and better for the environment. I'm still fairly sure it is better for the environment. But, although the leading causes of death in the US can be contributed to by meat, for me personally, vegetarianism was a poor choice.
I think there are two reasons for that. Body and mind.
One is that I am metabolically carbohydrate intolerant. There's actually a fancy and expensive test, at least it was expensive at Duke University's Diet Center. But basically it means that my body reacts differently to carbohydrates than the rest of the world's bodies do. Two ways. One, my body stores carbs much better than it stores anything else, even fat, supposedly. Two, my body thinks it hasn't eaten if I feed it carbs. You know that saying about eating Chinese and being hungry again in an hour? Well, that's how it is if I am eating carbohydrates as the main source of my calories.
If I eat carbs, I get sleepy. Almost sleepy enough to count as passing out. If I eat carbs, I get ravenous. I'm hungry, hungry, hungry and it doesn't matter how much I eat, I am still starving when I'm done. (Which I knew a long time ago, but I didn't act on it.)
Since I've been trying to eat balanced carbs and proteins, my health and quality of life have improved more than a hundred percent.
Literally last Christmas, I could meet you, talk to you for hours, really enjoy your conversation, and if I saw you again the next week I did not remember ever having met you. Scary.
Since I began eating protein more regularly, my memory has improved dramatically. Unfortunately, I don't remember if I met you last year, but now I will remember you the next time we meet.
So, though I know that vegetarianism does have a positive impact on the environment and can have a positive impact on other people's health, it's not good for me. It only took me five years to figure that out and be willing to work with it.