Sometimes a foreign experience helps a player see the light, and Terrence Williams wholeheartedly embraces that theory. The swingman signed a 10-day contract yesterday with the Celtics, marking his fourth NBA team. He got his release from the Guangdong Tigers of the Chinese Basketball Association Tuesday night, and responded like a man released from captivity. Though talented, Williams’ early NBA tenure has been marked by immaturity and an inability to grasp the ramifications of being on a team. But he hopes he has been reborn with this move. “How to be professional,” Williams said last night of his greatest lesson learned. “My downfall in my second year (in New Jersey), what made everything go downhill was not being professional. Young, 20-whatever, money and not really caring. I cared about playing basketball, but not putting the work into basketball. If you go to China for even a day, you learn how to be professional, because you want to come back so fast. That’s what I learned with these last two years.” It’s sounds as though Williams’ Chinese experience was, shall we say, extreme. “Extreme is a small word for that,” he said. “It was definitely extreme. I wouldn’t recommend it for you guys to be reporters over there.” As if on cue, a Chinese reporter asked Williams if he kept track of his old Guangdong team. “No. I don’t care about the CBA. I’m just being honest,” he said flatly. “I don’t care if they’re winning or what. Good luck. I wish them luck, of course.”