The tax cuts ARE paying for themselves hence the record Federal tax revenues despite the massive tax cuts. However, Federal spending also hit new records, this negating the effects of the record revenues and increasing the deficit. Spending will have to come down.
The problem is that we have no idea what revenue would have been like without the tax cuts. Would it be higher than the actual receipts? Lower? Nobody knows, so you can't say that the tax cuts are paying for themselves.
Which is why cutting spending is the most important part of any tax cut. And historically we don't do that.