I had a cockatiel for 25 years and she was such a character. It takes time and patience to earn their trust but once you have they will love you forever and are very affectionate. If your cockatiel is truly afraid of you or dislikes you it will draw blood when it pecks you - but sometimes they peck simply to communicate that they are annoyed by something and not because they want to hurt you - if they wanted to hurt you they would. They express their grumpy feelings by pecking/hissing and you just learn to understand their body language. Let them come to you, encourage them by talking and singing and whistling, let them whistle back and you will start to understand their mood by the whistles they make ie slightly nervous or wildly happy. If the bird is is skinny then leave it alone as that means it is nervous/scared - if it fluffs up it's happy. You can even tell when they are smiling by the contours of their cheeks feathers which sounds nuts but it's true. We got our cocktiel when I was 8 years old and we loved each other for 25 years, I remember her sitting at the top of my pregnant belly and nose-nuzzling me with her besk, she would literally sit there wuth her beak pressed against my nose, her way of cuddling, she often did that. She loved to be stroked - would gently peck if you stroked her in the wrong place - but if you did it right her eyes would flutter closed, she loved it. She would gently twizzle my earrings with her beak. She also used to sit their with one of her claws in her ear hole with a look of contentment on her face, so funny. She was totally devoted to her human family but any strangers would dice with death if they approached her, she would attack anyone she didn't know. When we first got her she was totally suspicious and bitey but after a while she grew to love us - she was wonderful and I miss her terribly.