Your subconscious mind is a million times more powerful than your conscious mind, and it impacts everything in your life.
You attract what you think about most. If self-doubt and negative limiting beliefs are the your dominant thoughts, then your entire structure is built on a faulty foundation. As a result, you end up turning on cellular genes that you don't want to. When you are in a state of love, the brain releases dopamine, oxytocin, vasopressin, and growth hormone, all of which are chemicals that enhance the vitality and health of our 50 trillion cells into the blood.
It's why people say about someone who is in love that they're "glowing"
The same is true with fear, anger, saddness, jealousy it releases chemicals associated with fear, which are stress hormones and inflammatory agents, changing the chemistry of our blood.