Otherwise, we could just sit and wait for death to come.
One of the main concerns of mankind is the meaning of life(at least, it should be). Why are we born? Why do we live? Why do we think? Why do we feel?
To live demands so many continuous and repetitive tasks, that to be alive becomes a huge task itself. We can survive about 4 to 6 weeks without food. If you don't drink anything during 3~10 days, you'll probably die. We must breathe at least 10 times per minute, or die in 3 minutes without air. Our hearts have to beat at least 60 times per minute, and with controlled intensity, to keep our blood pressure under normal values. According to Wikipedia, we must blink approximately once every two to ten seconds. And there are several other tasks an alive human body is constantly executing, and we just don't know. Above all this, our brains must be working fine enough to keep the whole machine in order.
What if you had to do all of these tasks consciously? To count and manage your heart beats and respiratory movements, to plan which enzymes will be used to break that sandwich you ate last night, because you were really hungry at that moment. Looks hard, huh? Imagine now if you had to raise each arm 40 times per minute, and shake your head with violence at least 20 times per day? And touch your nose with your toes once every 6 hours? Looks even harder, huh? Yeah, our body complains about being tired sometimes. And we get weak, sick, and old someday. And then, we die. All the effort to survive fails in the end. So, are we born... do we live... to die?

Yes, and, of course, no. We are born to live before death comes. And we live... Why? Is it because the other option is to die? Because we are coward? Because we are brave? Because we have to reproduce to keep the evolution of human specie, and prevent its extinction? Because we are curious and need time to learn and know?

I don't know the meaning of life. I never planned my birth, and I don't plan my death. Life is the "in between" of these events, and this is what I have now. Unconsciously, I do the same thing everyday, every minute, every second. Consciously, I have to be different. I have to think and feel. Make new plans and discard others. Make a decision then change my mind. Try and fail, then restart. Think once then think twice. Set priorities, and re-order them.
Satisfaction leads to lethargy. So, keep changing and moving on. Everyday, every minute, every second. Otherwise, I'd rather have been born a tree. Trees live longer than humans...

One day different from the other, and nights with different dreams.