Yes. Not really. I also procrastinate after school. I go on this website and help people, then when I try to study, I get another PM asking for help. This continues until 1 am. The cycle continues. Going to watch the Swans game, be right back.
One day I had a HUGE mind blank. I tried convincing the teacher that she did a question wrong and I said MISS! You're doing it wrong, "a third is greater than a half". I keep repeating this for 5 minutes. The whole class laughed. Spiral was never the same...
It's because you're human (no derision intended). Everyone goes through patches of forgetfulness. Once you do repetitive question and it's drilled in your head. There's no more point in continue doing it, do a variety of exam style questions. This will happen again in Year 12. So it's nothing you should be concerned with. Just keep persisting.