There's no internal battle, it's just you and the weights.
When it comes to running any reasonable distance on the other hand you'll find that your body is 100% capable of going the distance. If you've been lifting for a year and have your body fat under control I can guarantee you that you're capable of running a lot further than you think straight off the bat.
Probably 6 miles or more.
But the voice in your head will tell you otherwise.
"Slow down, we don't have to be doing this"
"You just hit the 3 mile mark, you've done good... just stop now"
"Let's call it a quits and run more tomorrow, you've done enough"
Most people will allow the opinion and the pointless chatter of that voice to hold weight.
That voice is your subconscious.
That voice, if listened to will ensure you never reach your goals, be they under the bench press or in the board room.
Ignore that voice and push through.
As I said, the endurance athlete is a master of his own will-power.
The endurance athlete only builds this will-power by ignoring that voice and telling it 'No!'.
Now get running and stay tuned for the big benefits of running for bodybuilders, coming soon.