This all boils down to basic issues. There are too many distractions in our lives, TV, Apps, Phones, McDonalds, Burger King, Fast Food, Work, Sleep, Pay Bills, Pay Taxes; Do this and do that; stay on hold whilst I waste 45 minutes of your life trying to sort out your utility bill and then these plebeians cut you off and it feels like life is just a game of the Board Game SNAKES and LADDERS https://en.wikipedia.org/wiki/Snakes_and_Ladders
To get anything done nowadays you have to literally shut yourself off. No TV, no phones, no facebook, no twitter, no kids annoying you. Truly you have to get rid of all distractions and have some quality time with yourself. That is the only way to write a manual and RTFM.
If you are writing that manual; do not consult other people as other developers will throw you a curve or throw a spanner in the works. Hence back to no distractions....... write out a draft in full and ignore everyone including your wife.
That is how you complete a cycle of action from start to finish. Once you have the full draft... editing comes later ;)
I hope that helps put some sanity back,