Most people have one day of the week that they dread more than others. For some, it's tempo day, for others, it's speed day. For me, it's long run day. Every Monday my team has a long run. Every couple weeks coach will increase the mileage and we have to try to find the "best" route to make it seem less miserable.
There was a period of time where every long run I would do, I would stop 1-2 miles in and sit on the sidewalk feeling bad for myself or walk back to the school. It wasn't the burning in my legs or the heat exhaustion. Instead, it was my mind. When I'd look at my watch and see that I was only 1.5 miles in to the 7 mile run, I would have a mini freak out and start to believe there was no way I could finish the run--even if I felt fine. After a few weeks of this battle: Brenna v.s long run, I realized I let the long run win every time. I was only giving up on Mondays, but I finally realized that even though I was completing the rest of my workouts, it didn't matter because I was still giving up once a week.
I know I'm not alone. Other people on my team have told me they have a "worst day of the week." The thing is, if you give up on that day, you're not getting the benefit you should be from the workout.
I started thinking of ways to make that one day I hated, more bearable. The first thing that I knew I had to do was to stop psyching myself out. Practice should be something I look forward to, right? YES. Practice should be a place where you let go of everything else in your life and just run. But I was thinking too much into it. On long run days I couldn't even focus in class because I would be checking the temperature and trying to think of a loop I could run with shade, and maybe a couple lights to stop at. Once I came to realize that the long run was inevitable and me thinking about it all day didn't do anything, I was in a better mood at practice and more pumped for the run, as opposed to dreading it. This applies to any workout of the week. If you don't think/talk about how hard it will be, you will be a lot happier.
Once I stopped psyching myself out, I started to set goals. For example, I'd tell myself I wanted to run 7:45 pace for 7 miles. 
Setting a standard for myself helped me finish the run because I felt I was running with a purpose. Setting goals for yourself on your hardest days will make you feel even more accomplished when you achieve them. Even if your last mile repeat is a couple seconds slower than your goal time, you can sleep knowing you got through the workout.
Another thing that makes that hardest day of the week better is staying positive. It sounds dumb. I still struggle to stay positive when I know that in a couple minutes I'll be dying, but it's worth a shot. Even if you're struggling, having a motivated mindset will make all the difference. My team mates and I always talk about how sucky the track workouts will be, and they always are. But I find that the workouts we don't dread as much, are never half as bad because we're going in to it with a better attitude.
The last thing I will say is that you know your body better than anyone. If you're injured or low on iron or whatever it may be, let your coach know. But if you find yourself thinking of all the possible excuses you could make on the days you hate the most, shut off your mind. Look at the persons feet in front of you. Look at a street sign 30 feet ahead and get there. Tell yourself you can do one more repeat.
The voice in my mind never shuts up with complaints and negative thoughts and excuses. I will admit sometimes I still do give in, but once I understood that I could silence the negativity and just keep running, I started completing my long runs. So don't give in when you think you can't go further, and don't stress about your hardest day of the week. Let this be the season of killing your workouts, not letting your workouts kill you!