First some fun facts about the durability of the penis.
The penis can take several hundred pounds of pressure to be torn off. It would take a powerful machine to achieve such force. The penis can take a few hundred pounds of weight on it. It has no bones and the only thing that can break inside of it are blood vessels, which are very durable. The penis can also take a few hundred pounds of squeezing. There is no way to accidentally hurt the penis using brute force alone.
If you have fear of hurting the penis than this is the place for you. If you do well enough there will even be a reward. The first set of lessons will be about tease and denial and the next set will be about physical pain.