you can choose your testosterone level on a daily basis, like choosing to get drunk or not. I can't imagine what that must be like.

You can do it. There are drugs that elevate your testosterone, and drugs that suppress it. I've tried both. I don't care for the suppression; it's like being tired. Elevation gives me insomnia. The effects of elevation probably depend largely on how quickly the drug you use is metabolized; androstenedione (the over-the-counter pro-testosterone in the US) breaks down quickly into DHT, and most of the bad effects of "testosterone" (baldness, aggression, prostate cancer) are directly caused by DHT.

Theoretically, a man could increase his health by taking an injectable synthetic anabolic steroid with a long half-life. This would suppress his natural testosterone, which has a half life around an hour, and replace it with something that gave him the benefits of testosterone without the harmful effects of DHT. AFAIK this is untested.