I like to think I'm fairly frugal on everything besides the TJ, but I know I'm not. I'm in a pretty good position as a 21 year old. No debt whatsoever and my retirement accounts are already growing, but I'm already looking at liquidating a lot of my investments and spending a significant amount of my savings on a diesel truck. I was in the right place at the right time and was able to buy in to a good amount near the bottom of the recent corona virus crash. And now I'm going to fork it all over for a truck I honestly don't need that much.
You don't take money to the grave when you die. As someone with 40+ years to retirement, I see spending money and enjoying it as a better plan than dying with a huge savings account. To me, it is a balance between enjoying your life and creating a bulletproof financial situation.
Before you do that do a time analysis on that money. At 21 you could invest in fairy aggressive investments and let them sit for over 40 years. Over that time you could expect a 12% or so return. Say that amount you'd take out to get that truck was 25K. In 40 years that would be $2.3M. What will that truck be worth in 40 years?
Also, if that money is in tax differed accounts you'll pay taxes at 20% + a penalty for early withdrawal.