second wind noun [S]
a return of strength or energy that makes it possible to continue in an activity that needs a lot of effort:
We started to feel we couldn't walk any further but when we saw the village in the distance we got a/our second wind.

[TahlilGaran] Advanced Learner's Dictionary ▲

second wind
energy that is regained after being tired
After we got our second wind we continued on our hike up the mountain.

[TahlilGaran] English Idioms Dictionary ▲

second wind
n.
1. The easier breathing that follows difficult breathing when one makes a severe physical effort, as in running or swimming.
After the first quarter mile, a mile runner usually gets his second wind and can breathe better.
We climbed with labored breathing for half an hour, but then got our second wind and went up more easily.
2. informal The refreshed feeling you get after first becoming tired while doing something and then becoming used to it.
Tom became very tired of working at his algebra, but after a while he got his second wind and began to enjoy it.

[TahlilGaran] English Idioms Dictionary ▲