How to tolerate pain and increase my mental indurance while i run a race (read details)?

okay well first of all... i know im not talented but i am hardworking and dedicated to my running XC/track and i want to learn how to endure pain as in lactic acid in a race because my coach says i am not running with pain okay and i believe hes rite .... i run the 800m and mile i think ill be doing the mile mostly now because im more on the distance side... okay so well me being afraid of pain ended up pulling a 5:51 mile in my county race which is horrible i did the dumb plan of waiting in the back to wait for people to get tired and start my kick untill i realized i was half way of being lapped... okay well next race i am thinking about going in the front i know i can do it... the thing is for how long.... i need to increase my mental indurance in order to not care about that lactic acid pain/fatigue i need my mental and will power to get stronger so during the race i could keep pushing myself not to give up and tolerate pain.... so yes please help me how can i increase my mental indurance and be able to tolerate pain... btw i ended my last two laps just a little over a min