So this is a big one. This happens only when you have body mind awareness and have practiced yoga for atleast a few years.

You know exactly how to shift the pressure so that the injured muscle doesn't get aggravated. Just because you have shoulder pain doenst mean you should not work out or stretch and strengthen your other muscles.

Till then just keep practicing with a teacher and let them guide you on how to modify the asana to accommodate your injury.

Quotes that inspire are almost all from the Bhagavad Gita

1. Your mind is a wild animal and can be brought under control only by Abhyas (practice or discipline) and Vairagya (detaching from the result)
2. When meditation is mastered, the mind is unwavering like the flame of a lamp in a windless place
3. Pain is inevitable, but suffering is not. Desire is the root cause of suffering
4. For one who has conquered his mind, a mind is best of friends, but for one who has failed to do so, a mind is the greatest enemy
5. When your intellect transcends the mire of delusion, then you will attain dispassion and then know of what has been heard and what is yet to be heard

So the books that inspired me are

1. A Million Thoughts by Om Swami
2. The Bhagavad Gita - Actually discussing this in a group
3. The ancient science of Mantras - Om Swami
4. The science of yoga - Anne swanson (loved to read about the anatomy)
5. Kundalini - Om Swami

This among others

This is really difficult. I am a yoga teacher, however my husband and son dont do yoga regularly. Till my son was 8-9years he did it watching me, but last 4-6years he was more into football like my husband.

Now at 14, he just told me yesterday that he will do yoga in the summers. I think his hamstring inflexibility and stress from exams was the trigger. Of course I was overjoyed.

Husband though - i think he just needs the right teacher. He did it for 2-3 months, but didnt continue after the teacher left.