I am a person who 90% of the time has a different perspective so please adjust.
The movie talks about the feeling of death coming to you and the feeling of love.
Life is not like a Mission Impossible movie where you are alive in the end always with little adjustment. Life is brutal. Nobody is gonna remember you unless you do a really big thing. Also, nobody in future will care about your sacrifices. The people around you, whom you love will be affected by you. Like, in the Normandy landings and the Battle of Stalingrad, people made sacrifices for their country. Families have been torn apart for the establishment of modern-day USA, and Russia which is without Nazis. All thanks to those people who died. The value of those American and Russian soldiers' sacrifice won't be felt by their generals. Only their families and their love could feel it. And today modern-day people will just remember these battles as events. ( I am talking generally, ignoring the Ukraine war)
Death is inevitable. And this brutal life will try its best to kill you. Hazel was lucky to find her love before her death. Also, life is short. You don't know when a car would hit you and you would end. So make it beautiful or end it by yourself because sometimes because of you, people around you will suffer.
Yeah, that's it. (honestly it was dark)