how to distinguish can and can't?

Belly

They're so alike that I'm often misunderstand them

The same happens to were and weren't. For example: somebody says" It wasn't me" I often interpret as "it was me"

 

It wasn't me = It was not me.

We  were there.

There weren't there. 

The words are just opposites.

 

 

Hi,
in can't you might or might not hear the final T. In any case, can is usually pronounced cun when it's not stressed. Look at these patterns:

You can do it. ("do" is stressed, can = cun)
You can't do it. (both "can't" and "do" are stressed, you won't probably hear the T)

When "can" is stressed, the difference can be heard paying attention to the vowel length.

You can! (stressed, the vowel is longer than in "can't")
You can't! (stressed, the vowel is shorter, it's like it's clipped at the end. You might not hear the T)

That's all.