Sometimes when I don't achieve a goal I feel the urge to try to make up for it by compromising something else. I plan to take the bus to an event, but I didn't leave enough time so I take a taxi instead of being late. Or I've scheduled my current task until 2pm followed by some exercise, but it's 2pm now and the task isn't done, so I skip the exercise to make up for it. The worst is when I plan to do something before bed, and then stay up too late when it takes longer than I expect. I like to think of these as "takebacks", because I'm trying to take back time that I've already given away.
Occasional takebacks can be reasonable enough. After all, being able to adapt to exceptional situations is very useful, and people usually build in flexibility to their plans for that very reason. But the danger is that the flexibility can hide systemic problems that would be obvious in a stricter setting. Maybe you never leave enough time for getting ready or always underestimate your tasks. However, instead of those resulting in obvious consequences like lateness or tasks not getting done, you end up spending too much money and getting fat and tired.
Another manifestation of excessive takebacks is the ever-slipping deadline. The project was meant to be finished today but isn't, so tomorrow you just keep working like crazy to try to hit the deadline for yesterday. If it's still not done, you just keep working, all the while convincing yourself that you're still trying to hit last week's deadline. Of course, the deadline is gone, there's no way you can take time from the future and put it back in the past. The right answer is to eat the missed deadline, make a new deadline based on the actual facts and proceed sensibly from there.
But it's easier said than done. Nobody likes to fail, especially because failures sometimes have serious consequences. Of course, the takeback has consequences too, but future consequences instead of present consequences so they're easier to ignore. All that time has to come from somewhere, though, and unfortunately the problem often cascades: a takeback from yesterday means not enough time today, which means even more takebacks to deal with tomorrow. And what about when a real emergency happens? All that flexibility you planned in is already used up by everyday takebacks.
For me, at least, I've been aiming for no takebacks. It might not always work out, but I think it's a noble goal. It's a hard, humbling thing to just say "I wanted it done by 2pm. It's 2pm, it's not done, and I failed." But in the long run it's better to have learned from a series of real failures than fake successes.