A Moment I Cherish in My Life
A moment I cherish in my life is when my children were born.
I remember the day my daughter was born, 15 years ago. I was very nervous, as she was my first child. Although the pregnancy went well, the first time is always a bit scary.
Fortunately, during my second pregnancy 12 years ago, I was able to enjoy it more, because I had already gone through being pregnant.
Ever since my children were born, my life has never been the same. I feel a profound sense of love and obligation in my life.
NB: "My life was turned upside down" has a negative connotation.
I've made stylistic corrections/suggestions, to make your text sound more like a native speaker's. :)