I attack my Sensei (When demonstrating a technique) pretty much the way anyone on the street would. Not because I want to prove a point, or that I want to test my Teacher, no.. just because, sometimes, you have to, It helps build more confidence, it refines your technique, and enhance the senses. Doing Aikido slow and secure all the time is great, but sometimes, speeding up things really give different results.
I also do surprise attacks on my Sensei (and other Aikidokas) in the middle of our practice, it's sooooo much fun!
Good for you, no guts, no glory. You find out what works and what doesn't. You don't learn much if you don't commit to your attack. Wet fish attacks yield little. Sure at first there are bumps and bruises sometimes on the receiving end of a give it your all real attack, but that is like any contact sport. You don't get thrown on mat as thick as a mattress, you don't build your cardio standing around playing touch tag. With a good hard attack your Sensei learns, and then you learn. Kudos to you!