Yeah, I procrastinated on this for years. What I did was:

- Created an email address at my own domain and forwarded it to Gmail.

- For the last year or so, started using it as my email address and changing accounts to use it as it came up.

- Signed up with FastMail and set up my domain's MX records to point to it.

- Still checking Gmail for stragglers to change over to my new address.

- Eventually will set Gmail addresses to forward, but didn't want to rush that so I remember to just make stuff not go to Gmail.

The hardest thing is getting used to folders again vs. labels. But FastMail has everything like filters and aliases and two-factor auth to an extent that... honestly makes Gmail look kinda basic.

The advanced features of Gmail were the most compelling reason to switch to it, but FastMail takes them a lot further.

I'm in a similar boat. I've used Gmail since its first year in operation. I started transitioning off it earlier this year, keeping it running as I've slowly migrated the vast number of web accounts that use my Gmail address as an ID, to use the new email address. With the benefit of hindsight I see that I should have registered my own domain and used that for all web registrations. Oh well. The final step will be to migrate my archive. I hope to be done by Christmas at which point I will strip all details from my account and then delete it.