It worked for mine when I showed him the math. " Look honey, if we save x% of our income, we only have to work for 9 more years! I think we can do it by eliminating x, x, and x, and saving more on x, x, and x."
And then I panted a very specific picture of what that would me. For us it is moving to the country, having a little cottage, and watching our chickens walk around. Yours could be anyting- travelling the country in an RV, spending time with your kids, volunteering. Whatever!
When it was a broad "hey we should do this so that we have FI" it was way too abstract for him to believe or focus on.
I also had to sit down and make a budget WITH him, talking about what he felt comfortable with and what he thought was reasonable. I was also very open when I had my own victories and failures with my budget, so that helped him. Openness was big.
That said, he still has hiccups. I just try to commend him for the successes and try not to get upset when he deviates from the budget.