… a.k.a a deadline.
Time-bound makes it definitive with a start-time and date and an end-time and date.
Deadlines are what keep people accountable and are what make people get things done. So by implementing deadlines for yourself, you’ll be more motivated to actually reach your goal within that set time-frame.
In saying all of this, make sure it’s a realistic time-frame, there’s no use in setting yourself a goal of running a 10km marathon next week when you’ve never run more than a metre in your life! You need to prepare yourself for this marathon! You need to train for at least a month, you need start at 1km and then build up to 10km, you need to practice running the 10km distance – even if you’re heaving by the end of it – then, and only then, you can run the marathon.
So, make sure that the time-frame is realistic. If it’s too short, you’ll be pushing yourself beyond capable means (and potentially entering cardiac arrest in the process which doesn’t sound like much fun to me!) and if it’s too long, distractions may filter in and deter you from your goal and you can lose motivation.