It sounds to me like you're already feeling the effect. You've expanded your spending and talking about spending still more. It's part of the consumer culture that we've been programmed by and are constantly reinforced to do. Tracking your actual spending for a few months may shock you.
Yes, you can "afford" to spend more and still hit your original FIRE date goal. If you love your job, then you might not care to FIRE sooner rather than later. If you hate your job or have things you're itching to do instead of working, then you'll be maximizing your efforts to FIRE as soon as possible. If an as early a possible FIRE is what you truly want, then you need to re-program your thinking and keep fighting influences that would swing you back towards the consumerist way of life.
I was raised frugal and was frugal for much of my life because I couldn't afford to be anything else. Then as my income crept up and eventually I had plenty of "discretionary" money, I started to spend more and more although always saving. It became a bad habit to just browse Amazon or store flyers to see if there was anything I "needed". It's taken a lot of effort to undo this and I'm glad I found MMM and the folks on this forum to help me.
Laura33 gave you a good technique to help (she and Cassie always give great advice). I found another helpful thing is putting off purchases as long as I could helps give me time to see if I really can use the item or if it's just a short term impulse or as a third option, is there a less costly route to meet an actual need (buying second hand or re-purposing something I already own).
You might find that up until now you'e been controlling your spendy tendencies by telling yourself "I can't afford that" which may once have been true. But now that you have plenty of money, your mind is less able to fight off desires. In that case, you need a new mental process. To fix my spendiness, I would still gothrough the Sunday flyers and mentally say to myself for each and every item I looked at ---- "I don't need that" or "I have enough of that" all the way through and it really undercut any impulse to buy SOMETHING, ANYTHING. It took months of this to re-train my brain and I still do it on occasion. But now I can check flyers or online store for what I need without being lured by non-essentials. Tuning out ads on TV or in magazines or the newspaper takes some training but helps too.
Without external pressures, you're just left with internal ones. Being achingly honest with yourself about what's really driving an urge means you can evaluate the potential purchase correctly. Want to update the kitchen so you can entertain more, for example, sounds good until you realize you don't really like to host parties. Maybe you do and yeah, an island with some seating would actually be genuinely useful. But does it need a marble countertop or would a fuss-free quartz one be the better deal in the long run.
I find that I can stick to my budget best if I allow myself a very rare treat, something fairly cheap, but that makes me really happy. Like a bouquet of flowers from the grocery store every 3 or 4 months for toeing the line. That and constantly reminding myself of my actual goals to ensure my actions match up with them helps.
The aim is not to be miserable but to cut out the wastes of resources that don't make our lives truly enjoyable. Only you can say what to leave in and what to leave out.
