One year ago I took a sabbatical, or a year of unpaid leave. My company permitted an employee to take up to a year off for personal reasons, and they would still provide health insurance, and some pension accrual. I "officially" gave my notice this month, and Wed will be my last day.
This past year has been amazing, it has been worth any small sacrifice I made getting to this point. While working towards FIRE I had several side gigs, saved as much as I could (my main salary), lived off the money the side gig money and met a preset goal I made for myself to retire Aug 2015, 20 years before traditional retirement.
The sabbatical was a sort of safety net transition/way of writing my own leave package. While it did feel like a had a little leash still attached (I told people I was on sabbatical, instead of retired) I think it was worth it. (Insurance benefit continued, pension accrual, I could go back if anything major happened)
For me, the biggest change is being able to control my own time. In my career I was at the mercy of my boss in terms of when I was at the office, no flexibility. I have been able to spend time with my family when I would have otherwise been at work, be able to travel to several foreign countries, climb Kilimanjaro, and bike tour the coast of Oregon. It has been a great year already.
So for those working toward FIRE, don't give up. It is worth it!