I also want to change myself but failed each time.

我也很想改变自己，但每次都失败了。

I couldn't help others change if I couldn't change myself.

假如我不能改变自己，那就不能帮助别人改变。

I want to change myself.

我想改变一下自己。

All I can do is change myself.

我所能做的就是改变自己。

Or leave, or change myself.

要么离开，要么改变我自己。