These practices are like positive thinking and meditation and they offer similar benefits.
Positive thinking is best practiced in daily life, visualization requires us to pause and dedicate specific time toward imagining a positive outcome.
Affirmations usually take some directed energy as well. It is helpful to write positive statements or to say them out loud.
Both techniques work to improve our outlooks in life and to rewire our brains into "solutions mode".
Reference- Food Matters
By Diane Gammon M.S. Clinical Mental Health Counselor