In terms of reaching a goal, I remember something I heard once that helps to keep me going in the face of adversity.

Whenever you accelerate in your car (or a roller coaster, or anything that can accelerate quickly), the law of inertia tries to keep us in the same place.  You can't see inertia, but you can feel it.  As soon as you start to move forward or go faster, you feel yourself being pushed back into the seat.  It's one of the ways that you can identify that you're actually moving forward.  You absolutely cannot have forward movement without inertia - it simply doesn't happen. 

In a sense, setbacks, obstacles, and resistance are the way to know if your goal is a suitable one.  If you met no resistance along the way, how proud could you possibly be of that accomplishment.  On the other hand, if you had to endure this, overcome that, and get through some other thing, there's something to write home about.

A body at rest tends to stay at rest and a body in motion tends to stay in motion. This concept applies to your fitness routine as well.

The other thing to know about inertia can be learned from the definition:

"A body at rest tends to stay at rest and a body in motion tends to stay in motion."

The word I want you to notice is TENDS.  This is great news because that means that it just happens in most cases, but not all.  So whatever resistance you're facing now can be overcome.  But don't think that this will be your last obstacle, you'll face many others that at the time will seem insurmountable, and you'll overcome them as well. 

Sometimes patience is your greatest weapon, like a caged tiger just waiting for that gate to be opened so you can pounce on your workouts again!