There's nothing to teach. You can't, as they say practice at the rift. You get one chance only.

10 seconds sound clip from the Supergirl (1984) movie soundboard.

You can hear this line at 01:42:43 in the Blu-ray version of the movie.

Quote context

[...]

- Why? (2)

- No, it wouldn't work. You'd be swept into a singularity if it didn't work. No.

- Forget I mentioned it. Have a squirt instead.

- I could do it.

- Then, please. At least teach me how.

- There's nothing to teach. You can't, as they say practice at the rift. You get one chance only.

- Sure? You won't have a squirt? Once you get used to it, I think it's delicious.

- You're right. You are absolutely right.

- There is enough doom and gloom in the air already.

- And it is better to accept defeat than to take a chance and try like fools to redeem ourselves and save our city and all those who we love there.

[...]