In order to excel at both strength and endurance pursuits, and in order to increase aerobic conditioning, we have to commit to a process. But, we don't want that process to come at a cost of quitting the exercise regimen we chose, simply because we engaged in it full throttle and then burned out after thirty days.
For some people, pushing themselves at the gym provides stress relief. But, if they push to hard too soon, push past their physiological limitations from the get go, well... kaboom. Hello physical therapy. By going that hard, that soon, they stand a high risk of not achieving their goals. Training can be intense but it doesn't have to hurt.
If exercise is not primarily about your livelihood, then it should be a healthy endeavor that makes you feel good mentally, physically. Instead of trying to prove how hard you are trying, it would be better to set consistent, realistic goals for yourself. Consistency should always come before intensity.
So how to find that line between making progress and overshooting? First, examine your value system. Consistency is the number one predictor of long-term success. In other words, to make progress, you need to be able to train repeatedly. This means that going to the gym on a regular basis is what is important. Wiping yourself out with one hard session is counterproductive since it can mean spending days having to recover.
Check out the following link for more detailed information relating to perceived exertion:
Consider your rate of perceived exertion, or RPE. If you're constantly near the top of the scale, you're most likely going a little too "hard" and putting yourself at risk for injury. Though it may not seem intuitive, the most direct path to fitness is by cycling through a variety of effort levels, with only brief spikes near maximal effort.