Life is

A training ground
- What is all this except a training ground for a reason which has examined with accuracy and scientific care all that life embraces.  (Marcus Aurelius - Meditation p.100)

of war,
- In a word, all that belongs to the body is a stream inflow, all that belongs to the soul, mere dream and delusion, and our life is a see, a brief stay in a foreign land, and our fame they're after oblivion. (Marcus Aurelius - Meditation p.15)

of decisions,
- Life consisted of a few simple signals and decisions; that death took root at the moment of birth and man’s only recourse thereafter was to water and tend it. (The Sailor Who Fell from Grace with the Sea - Yukio Mishima) 

of a dangerous caus,
- The real danger is nothing more than just living. Of course, living is merely the chaos of existence, but more than that it’s a crazy mixed-up business of dismantling existence instant by instant to the point where the original chaos is restored, and taking strength from the uncertainty and the fear that chaos brings to re-creat existence instant by instant. You won’t find another job as dangerous as that. There isn’t any fear in existence itself or any uncertainty, but living creates it. (The Sailor Who Fell from Grace with the Sea - Yukio Mishima)
- Personal reflection: Therefore there is no happiness in existence itself, living also created that. 

of creating your own story,
- Dad, is there any purpose in life? “ You see what I was getting at. or don’t you, what I really meant? Father, can you give me one single reason why you go on living? Wouldn’t it be better just to fade away as quickly as possible? But a first-class insinuation never eaches a man like that. He just looked surprised and his eyes bugged and he stared at me. I hate that kind of ridiculous adult surprise. And when he finally answered, what do you think he said?”Son, nobody is going to provide you with a purpose in life; you’ve got to make one for yourself.” (The Sailor Who Fell from Grace with the Sea - Yukio Mishima p.99)

it’s the choice to fulfill it,
- The goal of human life surpasses that of other animals even more than the one life suppresses the other, and what gives human life its greater excellence is precisely the great excellence of the goal it is ordered to. So it doesn't have to contain its ultimate goal in the way the lives of the animals do.  (Aquinas - Selected Philosophical Writings (Oxford) p.326)

it can be the activity of virtue,
- Life has two meanings: sometimes it means the living things very existence and that has to do with the substance of the soul, which is the source of existence in living things; but it also means the living thing’s activity, and in the sense, virtue disposes us to live rightly, for it is the virtue that disposes us to act rightly. (Aquinas - Selected Philosophical Writings (Oxford) p.400)
 
it can have different forms, 
- Clearly then there are three levels among the power of the soul, or living abilities: those of vegetable life, of animal life, and of rational life. But there are five sorts of ability: namely, nutritive, sensitive, intellectual, appetitive, and locomotive, some of these containing several powers under them, as we have said. (Aquinas - Selected Philosophical Writings (Oxford) p.135) 

it is less excellent then existence,
- And this is why pseudo-Dionysius says that though living things are more excellent than existent things, existence is more excellent than life: for living, things don’t only have a life but, together with life, have existence. (Aquinas - Selected Philosophical Writings (Oxford) p.208)

it is connected,
- Your life is like the ocean, everything runs, and touches, you touch at one point and it reverberates on the other side of the world.  (Fyodor Dostoyevsky - Os Irmaos Karamazov (Editora 34)

it is a miracle.
Life is not math, it is a miracle, everything is always different. (Herman Hesse - Kurgast)