For most people it is. Those who live life right is seems to fly right by, You have heard time flies when you're having fun. However those who make the wrong choices have to live with consequences it can drag on and on and on.
Iratus and Lady Wood came up with the right answer. You only gave a partial quote. It's usually used as "Life's too short to be angry / resentful / unhappy / or-insert-your-own-word. It means that since we only live once we should spend our time doing things we enjoy with people we enjoy and not to worry about trifles.
That doesn't mean we shouldn't work hard to make a good life for ourselves. Life may seem too short to work, but it's also too short to waste with no money because we were too lazy to earn it.
They didn't complete the sentence. Life is too short compared to how long other things stood. For example: Life is too short compared to how long the sun's life is. Life is too short compared to how long the universe's been here.
because we have so many chances, and opportunities, and different dreams, that collide with what society says we HAVE to do, and we never have enough time in this life to fulfill the chances and opportunities, and after this life, there is no more earth. no more chances, just up or down.