The Law of Attraction is an unerring, consistent force which organizes, or draws, precise vibrational frequencies together.
Everything is vibration; everything you see, everything you hear, everything you feel. Your thoughts are also vibration. Not only are your thoughts vibration, they are permanent, expanding entities of their own.
You are an eternal, vibrational entity temporarily focused in a physical body.
You, as a non-physical, source-energy being, made the decision to become focused in a physical body in order to experience the joy of physical experience and expansion. Expansion occurs naturally when you encounter something you do not like and, due to natural forces of the universe, you create the opposite. When you observe a situation you do not like, you physically launch a wave, like a sound wave, the opposite of which is the perfect, opposite, expanded evolved version of the disliked situation.
That energetic wave is actually the expanded version of you.
That creation is why the universe is continually expanding and also why the universe is eternal.
As a human being, in the moment you create the opposite of what you do not want, you experience negative emotion. That negative emotion is literally the feeling of resistance between what you do not want, and the newly expanded version of same.
In the moment you shift your focus away from what you do not want, by thinking thoughts that feel better, you experience a sense of relief which is literally the physical sensation of releasing the vibrational resistance between what you do not want and the newly created version of what you do want.
Everything in your life; your bank balance, your relationships, your health, is a vibrational match to what you habitually think. If you spend time feeling frustrated, you attract more things which feel frustrating. If you are worried, you attract more things that are worrisome. If you are appreciative, you attract more things to appreciate.
Your state of mind, your attitude, your mood becomes a set-point for you unless you purposely raise your vibrational set-point. See Raising Your Set-Point.