"This is too hard.  

"I can't keep doing this.

"What am I even doing?

We all have those thoughts.  It's human.

It's also in our human programming to avoid what is uncomfortable.  Our lives are a short sprint to experience as little discomfort as possible before we die.  The only problem is, the shortest and easiest path leads to more discomfort in the long run (for us, and the ones we love).  The only logical way is to endure some level of pain in the short term.  

Practice focus and discipline.  Have a vision.  It's tough, but we can do it.  Because here's the thing: each one of us is more capable than we think we are.  

It's true.

Here's the other thing.  The mind is always the first thing to quit.