You are very precious to me. Here are some sentences plus literal translation.
0-5 : 你真是我的好宝贝!(You are really a good baby for me.)
6-12:你是个好孩子,我非常喜欢你!(Good boy/girl, I like you very much.)
13-16:你很棒,我非常珍惜我们之间的友谊!(You are really excellent, and I do cherish our friendship.)