Hehe... when I was about 8 years old, my dad was letting me use an electric jigsaw to cut a letter "T" out of some wood.

My mom saw me holding the jigsaw and immediately confronted Dad. "He might cut his arm off or something!"

Dad said, "I think he'd stop before he got all the way through "

With the front brake, you don't HAVE to just "go all the way through" if the rear wheel is lifting. Either shift your weight to the rear by sliding back on the saddle (should be doing this already if you're braking that hard) or ease up on the brake to put the rear wheel back down.

let me add a practical piece of advice: find a steep grassy slope, like maybe a hill at a city park, and go down it slowly while experimenting with this. Apply the front brake hard enough to make the rear wheel lift, then ease off so it sets down. Or slide back off the rear of the saddle so your center of gravity is low and rearward, and observe how hard it is to flip the bike that way.