Wow, today was the first time I have ever worked up a sweat in the swimming pool. How do I know? Because I am still sweating now, as I write this. It's not like I was really working hard, but rather that I was working well. To give you some idea that my swimming coach has my best interests at heart, he cancelled the class saying that it was a better use of the time for me to just swim up and down and consolidate some of the things we had been going over, rather than to tire me out mentally with endless drills. This and the fact that I haven't been able to squeeze in any practice sessions in between classes. However, he said it as a positive thing - to take advantage of being on a roll - not as a negative consequence of not having done my "homework".
One of the motivational problems I have with swimming is that it is hard to tell how fast you are going or even whether you are improving. There are moments when everything seems to "flow" and you feel like you are moving forward with surprisingly little effort, but these moments are few and far between and as slippery as fish themselves: as soon as you realize you are touching one of them, they flit away. You get some sense from watching how fast the tiles scroll past but using other swimmers as a reference point is even more demotivating, especially if they are good. These days, now that I am using my legs more, I find that I am one of the swimmers moving fastest through the water and this, in a shamelessly self-deluding sense, helps me feel as though I am improving. But one of the best things about moving faster through the water is the bow wave that your head makes, neatly providing a "hole" in the water that you can breathe through without having to tilt your head too much. This is becoming my indicator of how fast I am moving.
The other thing that is hard to gauge in the water (and here I'm not even going to mention obvious things like body position, orientation etc.) is how much effort you or anyone else for that matter is making. There are ingenious pulse meters available that communicate your heart rate to you by vibrating your jawbone to create the illusion of a little voice in your ear. Maybe for my next birthday... For now, breathing is my best guide but even that can be flawed because it can be that I am not expelling the air properly between strokes and, in any case, the rhythm is dictated by the stroke rate. As for how hard everyone else is swimming around me, I should not care unless I am in a competition, in which case I can safely assume that they are swimming at least as hard as I am.