For me I did a lot of time management exercises like making an inventory of where I spent time in any given week and then planning the next week and seeing if I met my planned goals. That exercise is also good at showing you how much free time you actually have.

For me I often avoided starting tasks because I wouldn't have enough time to finish it before something else required my attention. Planning in advance shows that I usually do have the time, and if I didn't, I could plan to work on things in the slots where I did.

There are a lot of things they could say though, for me my ADD and poor behaviors when I was younger meant I needed a few things rebooted :)