The lecturer went on in the same vein, and told of some of his own chances which he had missed, as well as of some in which he had, to use his own expression, "caught on"; and he told some stories of personal experience so well that he made a lot of people cry a little.
The preposition -- or no preposition -- depends on the verb. The preposition is allied with the verb.
In the red part, 'which' is the object of 'miss.' We say that someone misses chances
. That's why there is no 'in' in the clause; we don't say miss
On the other hand, in the blue part, 'which' needs a preposition to go with 'caught on.' The phrasal verb is 'catch on to.' Usually we 'catch on TO something,' so, although the author uses IN here instead, we definitely need a preposition before 'which,' which represents 'something.' That was a great chance which / that / 0 you missed!
The chance which / that / 0 they lost will never come again.[
The chance to which Jack didn't catch on is lost forever.
There was achance which I caught on to, and I'm taking advantage of it.