I killed a part of me (which stopped be from XXX) to keep you alive.
字面理解是我为了救你而妥协。
Actually, it's from a love story which is starting with:
Yes, i killed it, i killed the part which stopped me from loving you,
The judgement was done, the heart was forced to suffer,
Suffer for loving you,suffer for caring about you,suffer for choosing only you.
...
直译是:
我杀死了我的一部分让你活着
我杀了自己一部分来拯救你