Yes, we definitely focus on one lifetime at a time. But I think Seth's point is that those past and future selves can aid us in this present one we're focused on. We can ask a future self for help with a problem it has solved. And we can send help back to the past when we were experiencing some difficulty we have overcome.

As for my past life, it was in late 19th/early 20th century France where I was a scientist who desperately tried to fight against the emerging pharmaceutical industry in favor of natural remedies but didn't succeed.

Today, you should hear me when a prescription drug commercial comes on TV. This industry's focus is on profit, disease, and suppressing symptoms with drugs that have ridiculous side effects instead of finding a cure and helping us maintain wellness. Also, I studied French in high school and it was my minor in college. And Dad was a scientist who taught us kids the scientific method at the dinner table. So while I'm into all things metaphysical, I like when science confirms it.