The past, the present and the future is constantly changing

 How is this possible?

We live in a Galaxy that has Time Travel Capabilities possibly like All Galaxies. So, those in Authority of this Galaxy change time lines for their purposes. On top of this there are criminals who also alter time lines. On top of this the UN changes time to prevent nuclear holocausts like the nuking of nations and the whole planet (just like what destroyed Maldek the Asteroid belt 65 million years ago).

So, if you understand that this timeline will automatically change because the past, present and future are going to keep changing then you can live your life understanding this.

From this point of view sacrificing your life in any war might not make any sense if you are thinking like a real Galactic Citizen tends to.

Because every Galactic Citizen likely understands that the past, present and future are constantly changing everywhere in the Galaxy.