if you want to write

And who doesn't? But I'm biased, as I can't imagine anything more wonderful than the written word. Okay, cats come awfully close. ;)

Three of the most delightful books on writing that I've come across over the years are Anne Lamott's insightful and rib-splittingly-funny Bird by Bird: Some Instructions on Writing and Life (which I'd recommend to anyone even if you DON'T want to write), Dorothea Brande's Becoming a Writer, and Brenda Ueland's If You Want to Write: A Book about Art, Independence and Spirit. The last two books were both written in the 1930's ('34 and '38 respectively), but are just as fresh and relevant today.

Brenda Ueland begins her short but effective closing chapter in If You Want To Write by asking the question, "Why urge everybody to write when the world is so full of writers, and there are oceans of printed matter?" (And just imagine how much fuller those oceans are nearly seventy years later!) "Why should we all use our creative power and write or paint or play music, or whatever it tells us to do?" she continues.
She answers by saying,

Because there is nothing that makes people so generous, joyful, lively, bold and compassionate, so indifferent to fighting and the accumulation of objects and money. Because the best way to know the Truth or Beauty is to try and express it. And what is the purpose of existence Here or Yonder but to discover truth and beauty and express it, i.e., share it with others?

Indeed. And well put. Um, excuse me; I have a few books to reread....

(quotes taken from Chapter XV111 pp. 176-9.)