After he comes back from the dead and resumes being Superman, Clark still feels empty inside, and he and Lois breaking up just adds to his silent despair. To fill the void, Clark finds some Kryptonite and makes it into a necklace or something along those lines. He wears it to feel human and them purposely gets himself into dangerous situations, like a Bar brawl, or even letting someone use him sexually.

When Metropolis no longer holds much thrill, Clark takes his dark habit to Gotham, where things are rougher. It turns out to be an almost fatal decision as he ends up getting beaten up in an ally and is about to have even worse inflicted on him. That's when a shadow appears and dispatches his attackers.

Just before he passes out, he hears Bruce's voice calling out to him in alarm. When he wakes up, he fully healed, but missing his Kryptonite, and with a very angry and worried Bruce wanting an
explanation.

When Clark finally comes clean about what he's been doing to himself, Bruce is appalled and also wracked with guilt because he feels that Clark is in such a state because of the savage beating Bruce gave him. Bruce in no uncertain terms tells Clark that his days of being so reckless with his own life are done. Bruce then takes it upon himself to get Clark back on his feet both physically and mentally. And it wouldn't be surprising if feelings develop along the way.