Can and Can't: entenda diferença na pronúncia

I often hear (in movies, series. ..) people say "can", but, actually, they say "can't". I just can figure out what they say (can or can't) because of the context.

I know that there is 2 ways of pronouncing "can't". In one of them, it's clear for me the 't' sound. But, on the other one (the most used), I can't even hear the 't' ... and for me sounds EXACTLY like "can".

Is there any tip that can help me with that? In other words, is there any piece of advice to help me distinguish between "can" and "can't" ?

Thank you very much indeed!