Speaking from bitter experience, I totally screwed up my life because I didn't plan for our care about my future because I didn't think I'd have one... Turns out I did, and decades of such neglect have had very serious consequences on myself and the people who cared for and depended on me.
With this neglect I dug myself a very deep hole that's been very difficult to dig myself out of, and now there are so many things I can't change and so many doors shut to me which were open to me when I was much younger and just even six months ago trying to change would have been sooo much easier and the consequences of failure so insignificant compared to today.
Basically, things just get worse and worse if you let them.