"Time is the enemy"

I've been going through a hard time lately. And I've been talking to a good friend who gives me good advice. And I understand everything except for this phrase. He keeps telling me that "time is the enemy".
Lately, I've been thinking my heart is the enemy of my head. And my head is the enemy of my heart. They completely disagree at this point.
One tells me to go right. The other says turn left.
I can't make up my mind. I honestly don't know which one to listen to.
But, as this friend surely insists, "TIME is the enemy."
Time never mattered before. Does it now? Do I have to save you in time? Do you have to save me in time?
I've always thought it best to think out my decisions and point out the good points vs. the bad points. But maybe I was wrong. Maybe I already know my decision deep down and I need to make my decision before it's too late. Maybe I'm running out of time.

Thanks for all of the talks, friend. They mean a lot to me.