1. I have made a mess of my life. I'll turn over a new leaf and live a better life.2. I know I've lied a lot, but you should give me a chance to correct my mistakes.3. I know I've lied a lot, and I promise you I will never lie again, ever.
 turn over a new leaf correct one's mistakes won't do something bad againturn over a new leaf = 把過去不好的地方改掉，重新開始，也就是改過自新
My sister is bad-tempered and would snap a anybody whenever she feels like it.