Migrating from Gmail to Fastmail is trivial. You literally log into your Gmail account from within the Fastmail interface, and it downloads/transfers all your mail. The only change that is unavoidable is a different e-mail address (unless you already use your own domain at Google).
You could literally change to Fastmail and cancel your Gmail account before tomorrow.
There are hundreds of excuses for not switching from Google or for staying on Facebook etc. But only one outcome: action.
I migrated from Gmail to Outlook.com a few years ago after I encountered a bug that I thought was serious but Google didn't. It wasn't that hard, but it did take some work over a period of time.
To start with, I forwarded all my Gmail to Outlook.com. As email came in and I read it, I would log into the site that sent it and change my email in there. As time went on, things slowly migrated out of Gmail. I told friends and family I was switching my email address but fortunately for me basically no human ever emails me. The few that do, I can receive the email at Gmail and send a response from Outlook so they get the update.
Now I'm about 99% migrated over, and the few stragglers that still send to Gmail make it to my new inbox anyway so I'm never missing anything.
You could literally change to Fastmail and cancel your Gmail account before tomorrow.
There are hundreds of excuses for not switching from Google or for staying on Facebook etc. But only one outcome: action.