"Want" is not part of the consideration. It's "need" that determines the outcome.
If you need me and even if you don't want me, I am here to stay. You can't get rid of me.
If you don't need me even if you want me to stay, I have to leave. There's no way you can keep me.
And this is how she works.
[想要]並非考慮的重點,重點在[需要]。[想要]在這裡只是加重語氣。
如果你們需要我,即使你們不想要留我,我是待定了!你們沒法趕我走的。
如果你們不需要我的時候,即使你們想要我留下,我還是非走不可,(因為我的任務已經完成了),你們想留也留不住我。
[需要]有如雪中送炭,[想要]有如錦上添花。