I'm afraid I won't be much use for advice in the military of Singapore, as they could have training regimens vastly different from the United States military.
I'd say just for a general point of view, just do as your instructors tell you to do. Don't let your mind tell you to back talk or not perform at 100% just because you might have a trainer or team mate who's a dick. I think you'll find that the more you just focus on getting each job done from a day to day basis and let that drive your focus, you won't find many things capable of distracting you from completing your training, which will carry over onto equal precision on the mission front, if it should ever come to that.
Secondly, drink LOTS of water. If Singapore is anything like American military, they will work you like a dog in the harshest of weather conditions, so proper hydration is probably even more important than mental precision. One of my friends just got a gallon of water and filled that up each day and went through the entire thing before he was done.
Finally, know your limits. Even with the combination of the above two pieces of advice, there are just certain things you won't be capable of completing. Always make a reasonable attempt, but if you're defeated, there's no use getting yourself hurt. A shamed soldier capable of learning from his mistakes without dwelling on them and completing the exercise later is going to be a thousand times more useful to the army than a soldier who hurt himself because he was too stubborn or proud to allow himself to accept defeat.
Thank you for posting this by the way, I appreciate the thought as Mod of the section. I wish you the best of luck.