It really sucks peeing when you've got a boner. Especially at 4 in the morning when you can't really think straight. Luckily this has happened before so I had the presence of mind on this occasion to sit down to pee instead of trying to aim an arc of urine from far away over the bathmat and into the toilet bowl. This method causes major splashback and results in lots of piss ending up on the floor, toilet seat back, and sometimes shower curtain and/or mirror, and/or my face.
But it's a delicate act, peeing with a boner, even while sitting down. It's painful- really painful to force your engorged member underneath the rim, where it brushes against the inside of the bowl (which is cold and revolting) and then having to lean way over so that the damn thing points down instead of straight out where it almost always manages to shoot out between the rim and the seat, which results in pee on your leg, underwear, floor, and possibly the door or wall across from the toilet, depending on how bad you really have to go. Sometimes in mid-stream it will get the better of you (it's a surprisingly springy contraption). You think it's resting safely and securely so you decide to risk reaching over for some toilet paper- and BAM! It pops out from your firm hold and relinquishes a torrent of pee on your hands and anything else in its line of sight which usually includes your face, chest, towels, pets, etc.
And even then, even if you've accomplished all of this, you will not be able to pee in a normal, free-flowing stream. You will have to pee in short, girly little bursts because it refuses to come out in a steady fashion for some reason- possibly because of the contortionist act you're putting your poor member in, bent down in such an unnatural fashion.
Eventually, after say, ten minutes of leaning over and pointing down, alternating between having the tip of your dick either against the toilet bowl or in the toilet water, pissing in squirts, you're finally done. And after you either congratulate yourself on not having pissed all over yourself and the bathroom, or you wipe all the urine off of your hands, face, towels, mirror, shower curtain, walls, cat, and any other place it probably hit, you give yourself a pat on the back and go back to bed, praying to God that you may never have to pee with a boner again.