Yes, there is an element of self-fulfilling prophecy or statements that are available to all of us. For example, "I will have a great day" as opposed to "This will be a lackluster day." "A winner never quits" as opposed to "I can't seem to get it right." And finally, "Maximize your day" is preferable to "This day has little potential." I don't know about you, but there is more positive energy and life-giving power in the more agreeable of each set of statements.
Having said that, the life-enhancing effect of what you say to yourself and to others is vital to the quality of life that we create. The popular lyric "I will survive" has given many women and men a push when things didn't go as they had planned.
Conversely, the opposite side of the coin is that less-than-perfect statements made to yourself or to others have negative potential that has to be witnessed to validate the downward spiral of its damaging causative agent, i.e., negative words. A friend told me 30 years ago that he had memories of his mother frequently telling him that he was a "bad boy." He started to believe his dear mother for whom he felt some affection and gradually became the bad boy she told him to be by her repeated statement. That bad boy is now a father and grandfather and is a useful member of society, but he had to shake his "bad boy persona" that was encouraged by his mother's words.
If you have landed here looking for a more traditional and spiritual element here's the personal affirmation I practice daily:
I believe God is forgiving me and healing me.  I also believe God is purifying me from all imperfections. In Christ Jesus' name. Amen.
- Psalm 103
- 1 John 1:9