I like the line about 'reaching further than your grasp'.
But I think it should be 'your grasp is further than you think it is'.

We walk a fine line between overachieving  and giving up.

We forget that we're only human.  In all our undertakings we have to remember to do the best we can while working within flawed and mortal human bodies and brains. 

We should try to be practical most of the time.  Pursuing the impossible is ok as long as  we remember that we may only get part way there and then someone else will have to pick up the baton.

Hi Ram,
I’m just reading Chrétien de Troyes’s legends of King Arthur and the knights of the round table (Erec and Enide), and it is all about wanting the impossible, looking for what nobody achieved before. These knights were not especially clever, they didn’t know where they were going and what they were looking for, but if it was something dangerous that enabled them to show their boldness, they were sure to try their luck, for no other rational  reason than that it had been impossible before them, and they might be the first to succeed where everyone failed before.
I grant you they were not very clever, and that these are after all just legends and real life is a thousand times more dangerous, but something about this way of thinking is so fresh and hopeful. They’d rather die young and idealistic than old and disillusioned. I think it’s a choice.

Great topic!
But, how do we know what is possible and what is fantasy?
From Taoism: I must know how to prepare myself without the need to act until events arrange themselves. Then, being prepared my actions can be in harmony and appropriate.
From Buddhism: Desire and expectation are the chief sources of our suffering. Joy comes from accepting reality for what it is and learning to navigate within it.
From True Hallucinations, by Terrance McKenna: (paraphrased) Thought moves quickly while the physical universe moves slowly. The way to manifest something is to envision it and hold that vision for a long enough period of time for the physical universe to organize around it. Meanwhile we must continue to live life.
From my own experience: If you feel like you are continually banging into a wall, perhaps you should step back and look for a door. Sometimes we are just not meant to travel a certain path. But, when our chosen path is correct life is easy and flows without hinderance.
And another: Opportunities are continually presenting themselves to us. If we are too narrow in our vision we blind ourselves and miss them.
 
A story: My sister, who is now gone, was two years older then me. For many years I watched her make one failed realtionship after another. There was a long string of losers, conmen and basket cases. Finally in her mid-fifties she met a man and found love and companionship. She was from NYC and was tall and stylish. He was from Oklahoma, was rough around the edges, was homely and shorter than her. They made a great couple. She said to me that she could never have imagined herself with him, because she had an image of the type of  man (tall, hansome, sophisticated) she was supposed to be with. It was only after she surrendered this imaginary companion that she could open her heart to the man who loved and cared for her at the end of her life. She gave up the "ideal" and accepted the "possible", which was in reality a great gift.

As a psychosomatic therapist I have a saying: True health comes from flexibility. Flexibility of body, mind and spirit. I don't know what is possible until I try. But, the rigidity of holding onto a dream, plan or idea to the exclusion of what is right in front of me, tugging on me, leading me towards opportunity and a possible happy and totally unexpected destiny is a form of blindness.