I am looking for the title of a book, I would have read it probably in the mid-to-late 70s, about a girl who was a budding tennis star and she was on the tennis competition circuit, but also coming of age and starting to have regrets or wishes she could be a normal kid. I distinctly remember a part in the book of the girl prepping for a tournament and having steak and eggs for breakfast, because it was high protein to fuel her. She wore her hair in long pigtails (as I did during that time). I don’t remember much more. The girl may have been blonde, but I don’t remember that either. Suggestion: When No One Was Looking by Rosemary Wells
Lost Classics of Teen Lit: Name That Book! 
“Heartbreak Tennis” by Amelia Elizabeth Walden – that would be my best guess. The main character has a sister who also plays competitive tennis; the sister has a pronounced scar on her face (it is revealed through the course of the story that the main character threw a glass or something at her sister’s face when she was a toddler, causing the scar, and her parents have really never forgiven her, to the point where they want her to allow the scarred sister to win at tennis in order to give her something to make her feel good about herself.) The main character persists with her tennis, and begins not letting her sister win at matches (parents get upset abou this)… as I recall, the book was written in maybe the mid-70s at the height of the tennis craze and obviously got a big following from girls who wanted to play.
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