Every writer knows there are two separate processes: writing and editing. To succeed, a writer must practice both activities completely independently of each other. If a writer edits while he writes, he risks paralyzing his prose with tense and strained sentences. If he writes while he edits, he risks disrupting the whole potency and order of his piece.
So too in life, there are two separate processes: working and reflecting. To succeed, one must practice both activities completely independently of each other. If one reflects while working, one won’t progress. If one works while reflecting, one won’t learn and improve.
Success in writing and life requires focus (doing one thing at a time) and timing (doing things at the right time).