It’s impossible to do it all
TLDR: “do your part” because it’s impossible to “do it all."
The short of it is: pick your battles. There are so many good and worthy causes and initiatives we can take up these days but you can't do it all. I recently read about a guy who was going fridge-free of all things! That would be a huge inconvenience in my lifestyle although I can see the benefits of it (save electricity and build consciousness around the food you consume.)
So pick your cause, your charity, your advocacy... Decide, in detail, how you will support it. Give yourself permission to do more or less if your life situation changes. And don't assume you will be putting your life force towards this forever.
As a personal example, I have not owned a car for my entire adult life. But I can certainly see a time in the future where having a car will enhance my quality of life to the point it is worth the cost (financially, environmentally and mentally.) Today, I don't have a car and I'm glad to walk, use public transit or ride my e-bike. Tomorrow, I may be budgeting for a vehicle and that's okay.
Someday, I will rescue a pet. But not now.
Someday, I will donate blood. But not now.
Today, I compost faithfully, choose vegetarian dishes at restaurants and continue to live car-free.
(Our RadWagon 4 e-bike)