What you have to ask before sacrificing yourself to preserve life as we know it is: Will my action make the world a better place?
Imagine this scenario: A vaccine is designed for a horrible disease that kills hundreds every year, and has a 5% fatality rate. With the help of this vaccine, the disease is eradicated entirely from the world, down to the last lab samples. The vaccine has a 1 in 1,000,000 infection rate. Nobody has the disease for a generation. This is undoubtedly a good thing.
After two or three generations, people barely remember the people who have died from this disease. It's history. The disease is non-existent. Evidently, vaccination is stopped, because the disease no longer exists. There is no point in risking lives when there are no recorded instances of infection in the last seventy-five years.
But then, someone is bitten by a monkey. Monkeys have never been vaccinated. This person has not been vaccinated. The disease spreads like wildfire: People have lost any immunity they had; the fatality rate is now 85%. Most of the world's population is killed.
You can never fully gauge the effect of any 'big gesture', i.e. any action that effects a lot of the world. The world is not a big truck on a straight road, where your actions are simply keeping the truck on the road. The entire area, as far as you can see is paved. You can drive in any direction you want. There will be bumps, but there will with most directions.
Life on earth no longer being 'as we know it' can be either a good or a bad thing. Take this into account when you decide whether to save life as we know it. Your 'leaving your mark on the world' may lead to massive death. Your procrastination may also lead to massive death.
Anyway, here's my point: You can never fully judge the effect your
actions will have. If you do something you regret shortly after, it could still have good (or bad) consequences. Think about this when deciding if you want to save
life as we know it.