I was 12 years old, 5 foot nothing and 25kg, which put me at a BMI of approximately HowAreYouNotDead?
My immediate goal every time I exercised was to either do more reps or do a harder version of a given exercise (eg moving from knee push ups to toe push ups, increasing ROM, using heavier dumbbells from within our small collection of not very heavy dumbbells). My mid-term goal was to not be able to see the ribs behind my nipples. My long term goal was to train in 100G and become a super-saiyan. Never quite achieved that one.