I can get caught up in some pretty doom-y thoughts about the future, and I do wonder sometimes if my fears that the economy will tank again soon, the stock market won't be reliable in the future, that my spouse will become unemployed, etc etc are incompatible with striving for FI. But so far my most powerful response to myself has been, "what's the alternative?"
Perhaps that might lead to a productive conversation? (I'm talking here about the 'striving' part, if FI is still years away; I'm assuming that the actual, "I'm FI now and ready to retire" question will take care of itself down the road, once the actual proof of income is there)
In other words, you've got expenses now, and the opportunity to save $. Saving leads to all kinds of security and buffers. What's the alternative? Broke and homeless because you never saved anything? If you're making investment decisions, risk tolerance, asset allocation, deciding on what you can afford to lose and how to plan for that, etc. can all be part of the conversation too. But those more detailed decisions could happen once the "let's save as much as we can to give ourselves options and security" idea has been sold?
There's also the "acting as if" philosophy. The, "you may be right, we certainly can never be 100% sure of anything in life. But if we waited for 100% certainty, we would never get in the car and drive to work! So let's 'act as if' the business cycle will continue, etc, and trust ourselves to deal with another eventuality if it comes to pass..."