Affirmations prime you for change by forming new connections, replacing old thought patterns with new ones. They strengthen you by helping you believe in the potential of an action you want to manifest.
‍When you verbally affirm your dreams and ambitions, you are instantly empowered with a deep sense of reassurance that your words/thoughts will become reality.

Affirmations alone won't manifest change. It's important to also take action in your life. For example, if you want to build your confidence, in addition to using affirmations, it's important to put yourself in situations that will grow your confidence like attending a social gathering and having conversations with new people, giving a public speech, asking for a raise. The combination of affirmations and action will manifest the changes you are intending.

Repeat affirmations a few times daily out loud or in your mind.
Consider writing your affirmation on a sticky note and placing it where you will see it throughout your day.

Over time, your negative thoughts will be replaced with your affirmations and change will manifest just like a caterpillar changes into a butterfly.