These phrases are usually said with good intentions, but hindering results.
The majority of goals are based around weight and looks or what we want to do right now when they should be based around long term quality of life and building your body to last. Don't get me wrong, it's quite alright to want the best body of your life right now. And if you're training to compete in any capacity, you should obviously do so accordingly. But don't let these things cause you to lose sight of what's truly important in the long haul. Doing so, can make life in the very near and distant future a living hell.
The first thing you need to keep in mind is that your workouts, be it in the gym, running, swimming, biking, etc, should be functional and make you feel better, stronger, healthier, more coordinated, and maybe even more confident.
If you finish a workout and feel like garbage, have joint pain or pain in your bones, or feel like you need advil to cope, something is wrong.
You SHOULD need a moment to catch your breath, cool down, have fatigued muscles, be sweaty, and feel like you accomplished something. You should feel like you're getting better, stronger and having more endurance over time. A day or two later, muscle soreness is ok. Joint pain is not ok.
If you're experiencing the problems previously listed, you need look into your routine and figure out where you're going wrong. It could be poor form, overexertion and attempting to do more than what your body is ready for, or an injury that needs addressed.
If you're injury free, talk to a training/coaching professional and tell them the problems you're experiencing and ask for them to assess your form to see if they can pinpoint where your issues are stemming from. The last thing you want to do is continue with potentially poor habits and develop a long term ailment.
If you have an injury, the following is extremely important for you to understand.
First thing is first. If you are suffering from an injury, pushing through or ignoring the pain and continuing is the worst thing you can do. Here's why:
1) Odds are, by pushing through the injury, you're making it worse. Even if you're not making it worse, you're not letting it heal. It will nag you until you stop doing things that aggravate it and let it heal.
If you compensate for it, you're more than likely to cause imbalances and other issues. For example, let's say you have a bad knee but you love running and refuse to take a few days to weeks off and continue the normal routine. "Grind through it" and you're pretty much guaranteeing yourself a knee surgery or replacement. If you haven't talked to someone who has a knee replacement, please do. They're not happier than what they would be with their original healthy knee. So again, think long term. Do you want to be sore and miserable with limitations for many years to come because you just had to run on your bad knee today? Trust me, if you let your injuries heal, and get back at it when you're fresh and recovered, you won't lose as much progress that you earned as you would if you worsen the problem for in the moment obsession and satisfaction.
Back to compensating to make it "tolerable". Let's say with the same knee issues, you want to do squats. Squats just kill that knee. So you put more weight on the good leg, or change your footing or alignment. You're giving yourself a fast pass to imbalances and probable issues with your hips, other knee, or lower back because now form is suffering. So now, just because you had to do squats with that bad knee, now you have more than a bad knee. You have bad hips, or a lower back, or two bad knees.
Pushing through partial tears and strains result in full tears and longer recovery time and even surgeries. Pushing through pains in your bones can and will turn into stress fractures. Don't let your need for instant gratification hinder your more important need for an abled body for the rest of your life.
2) If that wasn't enough, there's one more thing you need to understand while pushing through injuries. You're trying to lose weight and you have serious knee pain. But you're on a mission and nothing is going to stop you. So you push through this pain and run, lunge, and squat every day no matter how much your knee bothers you. Beyond making your ailment worse, there's a war going on in your body. Your brain is saying "I need to get this workout in so I can lose weight or build muscle."
But your body trumps your brain and says, "look here, I get what you're trying to do, but I'm going to release some hormones and block your weight loss. I have a bigger fire to fight right now to try and fix this injury before I can let this workout do what it's intending to do." At this point, your injury never really gets better, and you're working your tail off for results that your body will not allow to happen.
Now, just because you have an injury doesn't mean you should live a sedentary lifestyle. Just choose workouts that don't further aggravate the injury. If your elbow bothers you when you do tricep extensions, take a break from them and try something that doesn't hurt your elbow. Often times, tricep press downs with the palms down will allow you to work your triceps without stressing the elbow joint. If you love to run and your knees or hips kill you, have your running form assessed. If form correction doesn't change anything, maybe running just isn't right for you. Or maybe you can take some time off and heal and get back at it. In the meantime, try low impact legs exercises with ankle resistance bands or wall sits.
Feel good about what you're doing AND feel good! If you mix this with healthy eating habits, your body will follow and you'll be building a body to last for what is hopefully, a very long and fruitful life!
Lastly, if you are resting an injury and not doing anything that causes more pain, but the issue never seems to improve or gets worse after a couple weeks, consider seeing a doctor or accredited professional for corrective exercises and/or protocol to heal properly.