Hardening should not really be a problem - especially first thing in the morning. (This is when your qi is full)
However, if it happens to you while you are on the beach - or when wearing tight trous in a public place - if can be not only embarrassing, it can get you arrested.
So, should this particular hardening problem occur, the only thing to do is IMMEDIATELY dive face down onto the floor, feigning unconsciouness,* while thinking furiously of Margaret Thatcher and ice cold vinegar.
Hope this helps.
*The drawback here is, should a female turn you over and attempt mouth-to-mouth recussitation, you are in a worse situatoin than before.