Our thoughts are powerful influences on how we feel, how we see the world, how we see ourselves. Thoughts can't make a rainy day sunny, but they can help us be sunny under the umbrella.
Many things -- our conditioning, our personalities, how others interact with us, illnesses, beliefs -- affect our thoughts. Affirmations are intentional phrases that affirm a reality or viewpoint we want to nurture.
Maybe you've tried affirmations before, believing (as they're often touted) that affirmations are the answer for all ills if you do them "perfectly." Maybe they made you cheerful for a little while, and then life went back to normal. Maybe you tried them once, but they seemed forced.
There isn't a "perfect" way to do affirmations. Try different phrasings to make them work for you. For instance, when you're tired, try saying "I feel energized and alive throughout my body." Does that change the level of energy or does it bring up the contrary view? Maybe it will work better to honor the process, not the outcome: "I am becoming more energized each day."
For some, writing affirmations makes them bright in their mind. For others, speaking them aloud or into a tape player makes them resonate. Find the best way for you.— Susannah Seton, Sondra Kornblat in 365 Energy Boosters