Beeing vegetarian takes 0 time and 0 knowledge. Basically, every each of you can turn veggie today without a problem.
On the other hand, beeing vegan might take some time to adjust.
"We" will all be vegans in about 100 years, anyway.
Well, depression is pretty much an illusion, but that's not really helpfull.
Think about the stuff that makes you feel good to do. Spending your energy on daily basis will help. Eat proper and scream from time to time. Talk to someone, it'll make you feel like after happy pill you'd get at your...
Ride your bike, save the planet. And your health. :)
I got into cyclotouring about a year ago, still not sure about the next trips but that's something that stroke me like nothing before.