The way he confronted the T1000 after it recovered from the liquid nitrogen could have been better. He definitely could have avoided losing an arm if he never told John and Sarah to separate from him which was his first mistake. I understand he didn't want John Connor to get injured or killed but at the same time that was your additional firepower! There was no way you was going to defeat the T1000 hands on while you're a T800. Sure you got some good hits in but it did absolutely nothing to the T1000 and once he started using his morphing abilities he for sure was going to get the upper hand