I never knew Hishtadlus was meant to be such a deep, or complicated, concept. It was introduced to explain that although ultimately Hashem decides if you will succeed, you can’t sit back and wait for it to happen. I think JustARegularJew meant just that. You don’t know what Hashem has in store for you.
The Pasuk says, ??? ?????? ?????. The Mishna refers to Parnasa in terms of chasing it, ?? ????? ?????. The Gemara says that a person doesn’t know with what he’ll be Matzliach.
Knowing that all is in the hands of Hashem, you learn when to stop. When your opportunity starts to bump with Avodas Hashem, you know you hit the wall.
There is also a concept of getting the feeling when it is time to lie low. When there is a trend of failing investments, ?”?, don’t throw more money at it. Wait for a better opportunity.
And lastly, there is a concept of someone who has a level of Bitachon that he feels that doing more is not in line with Bitachon. This is a delicate aspect, being that it is all to easy to fool yourself. ???? ??? ??’ ????? ??? ???? ????. Yosef Hatzadik was taken to task for enlisting human help, whereas if one of us would turn down such an opportunity we would be called a Shota.
What your Rav probably meant was that there is nothing wrong with trying more, but if you don’t, it won’t be held against you as if you didn’t try. While it is important to do what you can, you also know what you are holding by. Past that point you defer to Hashem. Dovid Hamelech, who was able to fight went out to fight, and asked Hashem to help him win, Chizkiyahu, who wasn’t able, said, I’m going to bed and You save us.
Much Hatzlacha.