Here's what happened to me in the year or two leading up to my ER back in 2007-08.
I had developed a spreadsheet which included my current and projected expenses along with projected income from cashing out my company stock and investing it in a bond fund to generate dividend income to cover those expenses.
I also had in the spreadsheet projections for investment income and expenses going forward from age ~45 to age ~60 which is when I begin having access to my "reinforcements" which included unfettered access to my (Rollover) IRA, my frozen company pension, and SS, the latter 2 a few years after turning 60.
I had been working PT since 2001 but in 2007 had just reduced my weekly hours worked again, to 12 hours per week. This forced me to more carefully track my spending although I was still able to save a little.
In early 2008, I met with a Fidelity Account Executive to run my ER plan by. She entered my income and expenses into Fido's Retirement Income Planner (RIP) program and it confirmed what I had been seeing - if I get to age ~60 intact, the financial picture only gets better. The income line begins zooming upward as the reinforcements arrive while the expenses do not increase nearly as much. based on this, my AE said my ER plan was "good to go" and I could pull the plug on working when I wanted to.
I learned a few things from the RIP program and included them in my own ER spreadsheet such as using different inflation rates for different parts of my budget. I assigned a higher inflation rate to the health insurance premiums, for example.
As 2008 wore on, the remaining pieces of my ER plan fell into place. The financial markets were in free-fall that year, as you probably recall. But I quickly realized that this would become a huge benefit for me because what I would be buying was dropping fast while what I planned to sell (my company stock) was still rising. Still, when I pulled the plug at the end of October, it was still a little scary because it took a few days for the money to arrive, either electronically or via paper check. A week later, I had the check and the rest of the money was in my bank account and I returned to Fidelity to meet with my new AE process all the money, all of which went just as planned.
At the end of November, my first monthly dividend (i.e. my new "paycheck"), albeit a partial month, got posted to my bank account and any remaining anxiety disappeared. At has been smooth sailing ever since.