Is this sentence grammatically correct?

[BlackMax]

I'd like to know if I've used all grammatical structures properly:
What is unacceptable is to do what you don’t want and don’t need to – in this way you lose your valuable spare time you’ll never return back and will probably regret about it for long.
Thanks,
Max.

 

[bhaisahab]

I'd like to know if I've used all grammatical structures properly:
What is unacceptable is to do what you don’t want and don’t need to – in this way you lose your valuable spare time you’ll never return back and will probably regret about it for long.
Thanks,
Max.

What is unacceptable is to do what you don’t want and don’t need to do – in this way you lose your valuable spare time, you’ll never get it back and will probably regret it for a long time.

 

[BlackMax]

What is unacceptable is to do what you don’t want and don’t need to do – in this way you lose your valuable spare time, you’ll never get it back and will probably regret it for a long time.

Thank you for the fast response, but I wanted to use (and meant) the structure like [which] you'll never..., so that will probably... refers to the main part of the sentence. Can I use this form, or it's undesirable or requires additional punctuation? How would it sound correctly in this case?

 

[Barb_D]

... you'll lose valuable spare time that you'll never get back...

Is that what you mean?

 

[BlackMax]

... you'll lose valuable spare time that you'll never get back...

Is that what you mean?

Yes, it is.