In the oldie but goodie category is Anne Lamott's 1995 Bird by Bird: Some Instructions on Writing and Life about... both of those things.
I head about the book from author Chris Guillebeau who recommended Bird by Bird for anyone wanting to write better and found myself drawn to not only Lamott's views on writing but also her take on the world. I like interesting contradictions in people and Lamott comes across as religious (with her citing C.S. Lewis and his Surprised by Joy as an influence), profane, funny and with good insight. One thing that particularly stuck with me was how she seems to see the world with reverence and have that come across in her writing. At the same time that she write with wonder, though, she very much writes her world, with all it's warts.
In terms of the more nuts and bolts advice she gives around writing, the biggest notion that stands out is a writer writes. It's appointment work that requires putting in the time and good writing something that often can come when you just keep writing and then gleam the good out of the bad. The eloquent (and memorable) phrase used by Lamott is "shitty first drafts." Not to cause injury patting myself on the back, but this idea very much reminds me of the process of writing college English papers way back when... actually, just prior to the original publican of Bird by Bird.
Lamott also notes that if stuck on what to write about, someone should narrow down as much as possible (with the idea of "writing through a one inch frame") and just start describing. She recommends giving yourself short assignments about things as random as school lunches from childhood and people interacted with. The point is to just get started... with the Bird by Bird title coming from Lamott's father telling her brother how to get a report on birds done.
Just a very cool book that strikes me as a kind of (extremely honest, warts and all) love letter about writing by someone who has also taught classes on the subject. She also references the writer as a chronicler of events who stands apart and takes notes as things occur (or just occur to them) and the benefit of writing groups for people who take on this at times solitary pursuit.
Whether someone writes for a living, hopes to, or just loves to write, Lamott notes the reward for a writer in daily work done with devotion and commitment. It's not so important what's written and especially not important what the work starts out being (again, "shitty first drafts"), just to sit down, write... and then repeat the process.