Get enthusiasm on the cheap by buying a fancy wooden pencil to write everything down. A $3 pencil is now more exciting than a $2,000 computer. Many people will do the most mundane work just to feel a good tool fly.
Stay on paper as long as possible. Sketch and write things out long-hand, possibly even emails. We all know screens are distracting. It’s much more pragmatic to step away from them for a significant block of time than trying to learn an attentional jiu jitsu that may be impossible. If you think you can’t step away, do it anyway for one day to see how much trouble it causes. That’s useful information.
Have you ever written an email literally on paper first? I’m not sure I ever have. I like the idea though. If anything, I write it in another app (like iA writer) first, because for whatever reason the separation from my actual email app feels appropriate.