Effort Or Attainment: No pain no gain?
The broscience logic of 'no pain no gain' is hard to argue with. Not because it stands up to even the very slightest of examination but because arguing AGAINST hard work just sets you up to get shouted down for being lazy.
Hardwork and work ethic is probably a good thing and definitely shouldn't be criticised however that mentality has some serious negative consequences. The most basic is that it will put a massive number of people off from ever even considering getting involved in any type of physical training. If you believe a goal will require serious discomfort and actual pain they why would you ever opt in? Then for people who do decide to get involved the belief that pain equals gain will lead them down a crappy crappy path to either a loss of motivation or injury.
Seeing the 'gain' will always require some degree of effort (although hopefully not actual pain) in the same way that learning requires time spent studying and most jobs will result in some fatigue, either mental or physical, after a long day.
Now try to imagine believing that your success in school or work was purely dependent on how exhausted you could make yourself each day regardless of what you learnt or whether it was going to help you with a future test. Imagine scheduling your time each day and week in order to leave your self as ruined and burnt out as possible with no thought to the quality of your work. You would superficially appear to be a great student/employee but it is doubtful that you could sustain it for long or that you would achieve very much.
Instead think about what you are actually trying to achieve and about the requirements you need to achieve it. If your goal is to be 'strong' then what would the minimum requirements be? The ability to pick up something heavy up off the ground and the ability to put something heavy over your head... That would do it.
A great example of this minimalist approach would be Pavel Tsatsouline's Power to the People program. The PttP routine consists of five days a week performing a short warmup and then two sets of a deadlift variation and two sets of a press variation. The first is 'heavy' and the second is 10% lighter for both lifts. You start out quite easy and add a small amount of weight each day until you can't make all five. Then you lower the weight and cycle through again.
This allows all of your energy and resources to be put into making progress on the weight you can lift off the ground and lift over your head reaching your goal as quickly and simply as possible. Adding more sets or more reps to the program would actually slow down the rate a which you could make progress with the weight lifted. The extra effort would infact make the program less productive.
The same logic would apply to all goals (fat loss, muscle, speed, endurance or whatever else) although the method and program would probably be different.
Don't measure your success (in gym or generally) by how much effort you are putting in but by how much you can achieve.