Reaching your limits means you have to back off, so you can continue your way. However there are some situations that require you to reach your limit and breach it for the shortest amount of time.
For example at work you may be challenging yourself extremely hard, which is a good thing. This means you have to be in the red for some time, however there is also time that you have to rest. A great example for this is a truck driver they often have to drive very long hours and days to reach their destinations and to get back home. Which in turn will allow them to take a small amount of time off. If you continue this path day in day out, week in week out, you will be overreaching and be burned out in the future.
Once we accept our limits, we go beyond them. – Albert Einstein
Everyone has their limit, which is great for some situations. However there are moments that you should exceed those limits, even if it’s just temporary. For example eating healthy is good, but solely focussing on it is not sustainable. That doesn’t mean that you can’t focus on your health from time to time. Not having a cheat meal for an entire week isn’t detrimential to your giains. Especially if you don’t skip out on it for a full year.
Set yourself a goal and see if you have to enter your redline for it. One of those things you sometimes have to cross the line is achieving your education, obtaining your diplome. Some subjects are harder than others, some exams can be passed by already knowing the most of the information learned. For others we have to spend hours and hours to only grasp a small amount of it. Yet also for that exam you need to pass. Spending more time for achieving your goals is completely fine.