If you have psychological safety and develop a bond of trust with the person it is far less draining. Those things need to be developed and the working environment needs to make them possible, though.

I find that the fact that I rarely get stuck for long and the mistakes I make tend to get caught more quickly makes pairing vastly more productive in practice.

The productivity isnt directly in the speed of code output but the compounded effect over time of it being higher quality - meaning vastly less time doing post hoc debugging, bugfixing, reworking code, etc. It is invisible over the space of one or two tickets, visible over weeks and overwhelming over months.

At one company my pairing team routinely (and quietly) worked 9-3:30pm or 4pm while the surrounding nonpairing teams worked overtime and still delivered way less. If you can nail it it really is almost unreasonably effective.