My mum had the same attitude.
I was a hard working, high achieving model student and generally good all round. For perspective, I was the highest scoring GCSE student in the school in my year. I also took several a year early (I have 16 in total 😳) and even those I scored higher than the kids a year older who had had an additional years worth of teaching.
Was my mum proud? She never said she was. I vividly remember proudly telling her I got 99% on one exam, her immediate response was "why wasn't it 100%?"
At Sixth Form I went on to do 7 A-levels across three years. Again, despite studying hard (and also working mornings before sixth form and evenings after, in order to pay the rent she insisted I contributed), my best was never good enough.
I went on to go to a top 10 university studying a very specific degree - there were 12 places for my degree program, and I was given one of them.
And I crashed and burned. The pressure of all the years of striving to be perfect, trying to meet my mothers impossibly high expectations finally took its toll. I was burnt out. My mental health nose dived, I could barely function. I was suicidal, ended up under a psychiatrist for several years and all in all it took me a good 12 years to fully recover. And a big part of that recovery, was going no contact with my mum (as well as years of therapy)
Ironically, I am now successful and happy in my career, for which I have no relevant qualifications and my GCSEs and A Levels are irrelevant.
So my suggestion would be...
Celebrate your child's successes
Reward their effort rather than attainment
Don't pressurise