One thing that worked for me was pinning up my most attractive youthful picture, on my bathroom mirror.
The secret is that every cell in your body knows how to be that way, they remember.
Move, in your happiest ways, while remembering.
Laugh, even if nothing funny is going on. The deeper and more prolonged your laugh, the more your body loves it.
Stretch and flex, even if it is only your toes, exhaling gently and thoroughly on the exertion. You see, then you can't help but inhale deeply, using all your lung capacity. The oxygen from that automatically goes to the muscles just used. And, if those muscles are in your extremities, the oxygen has to pass through all the tissues on the way!
All the worrying in the world won't benefit you one little bit, you know that. So, have a giggle, even if it isn't yet sincere...your subconscious can't take a joke.
If you shout, "I am healthy...I am whole and well...I am beautiful!" - your subconscious has no alternative but to believe you! And, it is charged with serving up all the information, thoughts, and feelings to make well-being come true!
If a negative sneaks in, say "No." If a bad picture jumps into your mind's eye, pull a bullet proof glass between you and anything you don't like. All pictures belong to you. You may entertain them, or substitute them, or chuck them out, as you please. You are in charge.
In any case, happy things can never hurt.
You win!
My best,
fledgling