There are many ways of expressing the thought I think your are thinking! Here are just a few:
I washed his right hand and then his left hand.
I washed his right hand first and then his left hand.
I washed his hands, first the left and then the right.
I washed his right hand first, and his left hand second.
I washed both his hands, first the left and then the right.
I washed his hands, left then right.
I could go on, but I won't. My point in giving you so many options is simply to demonstrate the multiplicity of ways in which you can say--in English, anyway--basically the same thing.
Many past participles can be used as adjectives to say the same as "that has been X".
This is the best beer ever created.
However, been generally does not work like that, it's used only in verb forms.
This is the best beer ever been
So, you have to use a phrase beginning with that instead. Typically the subject of the previous clause is close enough where you don't have to specify the subject again.
This is the best beer that ever was (or has ever been).
It's the best of me that has ever been.
Grammatically this is OK:
it's the best of me ever being.
The problem is that to be means to exist, but nothing much more than that. So the meaning of being happy with one's life doesn't really come through, you're just saying you are existing in the best way possible. Trees and other inanimate objects do that.
I'm the happiest I've ever been with my life.
is probably what you want to say.
Best Answer
in your hands is a set phrase in this context. Makes sense since it is unlikely you do many important things with only one hand.
So:
Or a famous insurance company slogan: