Sex therapy can be complicated. Fortunately, sometimes it isn’t. About three months ago my patient Sam finally started dating again after his wife left him last summer. After a few nondescript experiences, he met Yolanda, they hit it off, and a few weeks later he found himself in bed with her. Two days later he came in for his weekly session. Five minutes before it ended, he mentioned how he couldn’t “y’know” when he wanted to “y’know.” “Oh,” I said. “You didn’t get an erection when you wanted one?” Yes, that was it, poor guy. I knew he wasn’t taking…