Every target is "CONQUERABLE"
We forget the fact that "every machine we face during our practice or examination has a vulnerability and can be hacked one way or another". So all we need to do is to step back whenever we feel like we've hit a wall, banging your head against the wall is good for nothing. Instead you can take a short break; get up from your desk and maybe grab a cup of coffee.
This short break will definitely help you to remove the clutter from your mind, also I would advise you to recall each and every step you performed on the target. From the reconnaissance to gaining shell on the target machine, you have to look at the details of each and every step.
Don't assume !!!
As a seasoned penetration tester, we all might assume that a particular service might not be vulnerable at all. Trust me I've been there and put myself straight into rabbit holes just because of my assumptions about services running in the target machines. I don't want to go in details about this, but I strongly recommend you to perform the checks you have to do, without any assumptions.
Celebrate small wins, they are important !
"OSCP is not just about the goal, It is the journey what matters the most".
Don't forget to celebrate short wins while you transform yourself from a pebble to a boulder. Make weekly goals rather than monthly goals and achieve them to celebrate your victories frequently. And that will keep you motivated during your preparation phase.