I don't know the weight balance of that trike, but the picture of it looks reasonable, i.e. you're not too close to the front axles. In that case, yes, it sounds like inexperience. Practice your braking in a safe place. Stop gently, then progressively harder. You have to learn to control your brakes. This is what I teach when I teach cycling skills. On a regular bike, the risk of tipping over forward is real but small, if you can control yourself. Also, you should have some "spring" in your elbows when you brake hard.