Been vegan for close to a year. The negative environmental impacts of the livestock industry are irrefutable, the morality of raising/slaughtering sentient animals is questionable at best (especially when we don't need meat/animal products in our diets), the negative health impacts of animal/dairy products are backed up by scientific evidence.
Practically speaking, millions of people are thriving on a vegan diet. And you see a lot of vegans among athletes, such as endurance athletes (ultra runners) and bodybuilders. Both need to be lean as well as strong/fit.
Iron deficiency is common in the general population (30% of the global population), not exclusive to vegans by any means. There is disagreement anyway about the minimum recommendations for iron. Iron can be easily supplemented (vegan supplements) if needed.
I highly recommend checking out Nutritionfacts.org for scientifically-backed, study-based health info.
Personally speaking, I went vegan and immediately dropped 7-8 lb on an already lean 125 lb frame (previously was pescatarian for awhile). The extra fat that I could never get rid of, even through strict calorie control/exercise/hungriness, just melted away on a vegan diet. Now I eat as much as I want, whenever I want, and am never hungry. And I sleep better at night knowing that I don't support the livestock/dairy/fishing industry. There has never been a better time to go vegan with so many food options out there. If you're a foodie, IMO the vegan diet is the ultimate diet because you can eat as much as you want without gaining weight (assuming you don't eat a lot of junk/processed food).
My only regret is that I didn't turn vegan a lot sooner. Not just for my health but for the health and education of my family.
I'd be happy to offer more advice offline if you want to send me a PM. (I won't be responding to trolls if this turns into the usual NBR gong show. The hardest part of going vegan might be dealing with the same old misinformed/trolling arguments--humans have canines, humans are top of the food chain, we are made to eat meat, plants are intelligent/feel pain too, agriculture kills animals too, blah blah blah.)
Edited for clarity.