In no particular order:
*having a savings plan. Before really diving into this lifestyle, I'd always been a 'saver'. At a rate of about $200/month. I was just saving money because that's what you did. I didn't have a plan for emergencies, monthly spending, or a plan to FIRE.
*letting go of aspirational spending. Spending money on hobbies or pastimes that aren't really me, just because I thought that I would someday be the person who knits handmade gifts or golfs.
*turning down invitations to do spendy things. I've tried inviting people over to my place, as Mustachians and the Frugalwoods suggest, but with limited success. I still want to hang out with friends, hear live music, and try new things. It just requires more thought and planning.
*planning. I love theatre, and in the past I'd justify orchestra seats to a traveling Broadway show because "supporting the arts!" "amazing production values!" "might never see this show again!". Now I look at schedules for the community college and local productions. If there's an amazing show that I really want to see, I'll check out these options first. I also let it be known that I LOVE going to shows, so I'll take your tickets if you don't want to go. I've gotten to see three big shows that way, plus countless arts festivals and food shows. If there's no money in the spending plan, I'll have to forgo this time. Which leads into...
*FOMO. In this great big wide world, things are going to happen. If I miss out on this one, there will be another thing. And if I spend all my money on other things, I'll have to wait until the next thing comes along that I can afford. Something else always does. I've found that I'm more grateful for time spend with family and friends than for paid experiences.