A life with no meaning is emptiness. We need meaning to motivate us to do things like save the planet from ourselves. Meaning gives us purpose. All living things have the same purpose. Some believe the meaning of life is to just enjoy yourself. The "pursuit of happiness" though is hedonism which is a vacuous dead-end. The true meaning of life is evolution. An orange seed, not being very sophisticated, possibly cannot see its purpose in life. Some of us, being much more sophisticated, clearly see the purpose of an orange seed is to grow into the best orange tree it an be. You do what you can to improve yourself and the lot of others. Of course, evolution does result in a lot of dead ends but none of them are vacuous. Evolution is all about trying to make something better given what there is to work with. Sometimes the evolutionary path doesn't work out but the important thing was the attempt.
Evolution is a property, a fundamental
driving force of the building blocks that
all matter is "made" of. In genetic evolution the improvements are
stored in genes. Note that recent
discoveries in genetics show that an organism's environment can
actually change our genes which are passed on to the next generation.
In cultural evolution the improvements are stored in
books, art or passed down through teaching. Evolution is the drive that
makes us want to continue living. The whole purpose
in life is to improve yourself and the lot of others. When you do this
you are happy. When you get mired into feeling sorry for yourself and
dwelling on the past you subvert this drive. As a result you get
depressed and want to die. To save yourself from this chasm of hopelessness you must force yourself to begin evolving again.
The meaning of life can also be looked at as loving and helping others. Others don't just mean other people but other animals, even the entire system of nature, the Earth. When you love others unconditionally you are helping them by making them feel better. We all feel good when we are wanted and are perceived of as being special. When you help others you are doing what you can to reach a higher level. You don't have to be a saint to do good. Start small. Smile at people. Forgive someone. Hold open a door for someone. Stand up to a bully. Feel compassion for those that intentionally hurt you, they are sick or emotionally stunted. Recycle and compost. Learn something new. Walk or cycle instead of driving.Note that you have to take care of yourself too in order to best help others. You can't just work at improvement all the time. You have to take some time for yourself to appreciate the beauty of world around you. Taking it too far is hedonism which is immoral because you are squandering time and resources only on yourself instead of others. Things like living just for living, experiencing the experiences life throws at you, enjoying the people, places, cultures you encounter is fine in moderation but basing your life on just that sort of thing is hedonism which is empty and meaningless. Hedonism is the reason that we are in the process of killing ourselves due to pollution.