Student or Learner
The Grand Canyon hike is one of those things you have to try to really understand. It is difficult at times but truly was adventure of a lifetime. It is an accomplishment that I will always remember with happiness and pride.
Add 'the' before 'adventure'.
The first sentence is a little ambiguous. Do you mean:
The hike is something that you must try. If you try it, you will understand it.
The hike is something that I want to you to make an attempt at understanding.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.