Don't feel bad to be beaten by kids, and I got beaten by my wife

I can do all 4 styles, but just can't do anything well.

Flexibility is important, and weight matters too, so those kids already triumphed over you in those 2 categories by default:)

Speaking of free style, I guess maintaining your balance is critical, so that you don't waste energy. You need to 把动作做到位，turn your body but not to shake your body.

看孙杨1500米的时候，NBC解说员就不停地夸他踢腿的规律性与力度。