Decide something
Decide for once
Once decided, then don't look back
Go for it.

No point in it
There is no point in discussing over something, which has been decided prior.
Agreed that it won't be possible to give your best initially in the first instance itself, however, something is always better than nothing.

What's the harm, if better is achieved initially in the first instance itself
At least you will know and understand where you stand
So forget the rest and go for what has been decided prior.

Give your best,
think of the best,
definitely you will achieve better,
if not the best.

So before getting anything done, it's always better to decide first.

Decide something
Decide for once
Once decided, then don't look back
Go for it.