How to find motivation to overcome a hindrance in the moment of truth?

I am trying for a long time to find motivation to practice meditation - i think i found a good general motivation finally after watching a dhamma talk but it still doesn't fully solve my problem : when i have the hindrance show up - how to overcome it ? hunger - tiredness - pain - cold ect now people can say : "just be mindful of it and let it go" BUT ..... **how do i find motivation to be mindful at that specific moment** ? i can be mindful for half an hour meditating being mindful but what should i do when i become very tired or very hungry - where its very hard to stay mindful - what gives me the power to overcome it than - how to find motivation to be mindful at that specific hard moment ?