我就以“我会亲自去做这件事的”为例吧.
I will do it by myself 口语可以缩略为I'll do it myself
还有一种不用oneself的说法
I will do it on my own
另外
One oneself does sth.是可以的.
举两个例子
“你应该亲自参加这个实验,而且还要以实验一部分的身份参加.”
You yourself should take part in this experiment as a component.
“他手下的杀手都失败了,所以他只好亲自动手暗杀了那个特工.”
He himself assassinated that agent because all his stupid killers failed.