Second wind is an American idiom for the life force that kicks in, in the early morning hours, when you are about to give up in exhaustion, that keeps you awake and able.
It's a refreshing feeling that comes about after you feel tired doing something then get used to it.

A 1985 pop song by Billy Joel that also goes by the alternate name- You're Only Human

You're having a hard time and lately you don't feel so good
You're getting a bad reputation in your neighborhood
It's alright, it's alright
Sometimes that's what it takes
You're only human, you're allowed to make your share of mistakes
You better believe there will be times in your life
When you'll be feeling like a stumbling fool
So take it from me you'll learn more from your accidents
Than anything that you could ever learn at school

Don't forget your second wind
Sooner or later you'll get your second wind

It's not always easy to be living in this world of pain
You're gonna be crashing into stone walls again and again
It's alright, it's alright
Though you feel your heart break
You're only human, you're gonna have to deal with heartache

Just like a boxer in a title fight
You got to walk in that ring all alone
You're not the only one who's made mistakes
But they're the only thing that you can truly call your own

Don't forget your second wind
Wait in that corner until that breeze blows in

You've been keeping to yourself these days
Cause you're thinking everything's gone wrong
Sometimes you just want to lay down and die
That emotion can be so strong
But hold on
Till that old second wind comes along

You probably don't want to hear advice from someone else
But I wouldn't be telling you if I hadn't been there myself
It's alright, it's alright
Sometimes that's all it takes
We're only human
We're supposed to make mistakes
But I survived all those long lonely days
When it seemed I did not have a friend
Cause all I needed was a little faith
So I could catch my breath and face the world again

Don't forget your second wind
Sooner or later you'll feel that momentum kick in
Don't forget your second wind
Sooner or later you'll feel that momentum kick in

A 2000 country song by Darryl Worley/Steve Leslie

There's an old friendly breeze that blows in the Gulf of Mexico
Somehow it always knows when I'm feeling low
So I'm gonna anchor down and wait till it comes around
Leave the rest of the world behind,
Yeah, that's how I'll pass the time

Till I catch my second wind
Get back up and gain control again
Find the strength I lost back when you stopped loving me
I guess I'll just stay out here until I know the coast is clear
Sit and watch the tide roll in
Till I catch my second wind.

There's a peace in the way I feel when the water's still
And as long as it's calm out here I've got time to kill
But as soon as it starts to stir I'll lose track of the way things were
Float away on the open air, but I'm not going anywhere

Till I catch my second wind
Get back up and gain control again
Find the strength I lost back when you stopped loving me
I guess I'll just stay out here until I know the coast is clear
Sit and watch the tide roll in
Till I catch my second wind.