Wh-cleft clauses

[ARUK2008]

I'm reading about What clauses and I don't understand why these sentences are written as follows:

"What you don't understand is he's happy enough as he is."
Couldnt I say "What you don't understand is THAT he's happy enough as he is"? If not, why?

"What you need to do is find something to occupy your time."
Couldn't I say "What you need to do is TO find something to occupy your time"? If not, why?

Thanks for your help!

 

[Barb_D]

Yes, to both. Those changes would be fine and not change the meaning at all.