Exhaustion, muscle tightness, rapid heartbeat, and sweating profusely describe the physical nature of two things that comes to mind.
1. You are having a panic attack.
2. You are working out with Supreme 90 Day Total Body.
Well, for me it was the later. The entire time I was working out, I felt like I was having a panic attack because I realized that I was forgetting to breathe. Yes, I would forget to breathe. If you are wondering how someone could forget to do such a simple task, it is easier than you think. When working out you sometimes find yourself holding your breath, especially during resistance movements. Mentally you brace yourself to take on weight against gravity, you take a deep breath, you do the movement, you complete the movement, and your set is finish. Guess what, you forgot to breath out. Breathing in is very important for oxygen intake to muscles, but breathing out is just as important for carbon release. The next time you workout remember breathing is a part of the workout. What I do is match my breaths with the exercise. For example during squats, I breathe out when squatting down, and breathe in when squatting up. This may be challenging in the beginning, but you will notice later during the workout you will have more energy to complete.