Worse yet, if you are young and at that working stage in life where you are supposed to be saving for retirement (and this is not optional, for all of us except those few lucky folks with pension plans), the real damage might not be realized until far later in life - when you wake up one day, at age 40, and realize you really have no real plan in place for the rest of your life - if indeed you had any sort of plan for the first part of your life, other than to go to work today and maybe spend money on something.
And the problem is, the "small mistakes" issue never freaking ends. I think at this point in my life, I am pretty immune from spending $300,000 on a motorhome or some other big-ticket purchase that could end up causing a lot of financial pain. And student loans were paid off a long time ago - with no prospect of them intruding into my life again.
But the spending aspect - that is a continual battle on a daily basis. It is like dieting and exercise - something you have to be vigilant about all the time, or weight just piles on.
And I can say, honestly, that on both fronts, I have fallen from grace, time and time again. It is all-too-easy to spend a little here and a little there and then realize at the end of the year, that you are spending more than you thought you would, which in retirement, can be a scary thing, as you have only X dollars to spend for the rest of your life, with little or no prospect of Y dollars in income coming in.
In other words, there is no point in your life where you are "wealthy" and can then stop worrying about money and spending. Even if you win the lottery - especially if you win the lottery - you have to keep track of spending, or end up broke within a few years.
It sounds depressing and anxiety-inducing. And to some extent, it is. But getting your financial house in order - and keeping it that way is really essential for long-term happiness. The relief from stress in understanding your finances is far greater than the nagging doubts one has by ignoring money issues.