Avoid Overstepping the Boundaries of Trust

Gemara: Rav would not pass in a ferry in which a non-Jew was sitting, as he would say: "Perhaps there is a decree upon him, and I may be affected along with him." Shmuel would pass only in a ferry in which a non-Jew was sitting, as he would say: "Anger against the members of two nations will not have dominion." Rabbi Yannai would check [for holes in the ferry – Rashi]. Rabbi Yannai was consistent in his approach, as he would say: "A person should never stand in a place of danger and assume that a miracle will happen to him, for not always is a miracle done for him, and if a miracle does occur, it is subtracted from his merits."

Ein Ayah: There is no characteristic in the world that cannot be corrupted by people, in which case it can cause an opposite result to the desired result of the characteristic. Therefore, great people must be a positive example in the way they lead their lives to show how to follow a straight path. That way, others can learn from them the characteristics and proper manners, as they remain within their appropriate borders and their essential purity.
One of the holiest attributes is that of bitachon (trust) in Hashem, which should be ever increasingly present in a person’s spirit. The purpose of this bitachon is to draw people close to Hashem. This itself is a great realization of personal completeness and a manifestation of the power of spirit to follow the strength of Hashem in times of need, when a person consistently finds refuge in Hashem’s protection of him. Even when all natural factors are powerless to save him from a negative fate, the power of Hashem will give him strength.
Still, a person has to be very careful that this special attribute ofbitachon should not become a destructive force. Specifically, it should not encourage him to be lazy and inactive, which are traits that are antithetical to true human completeness. Therefore, the closer a person is to Hashem and is fortified with a high level of bitachon in Him, the more he should be vigilant and diligent in regards to actions he is expected to take. This helps ensure that the entire nation will know that the glorious crown of bitachon, like all holy attributes that stem from knowledge and pure fear of Hashem, will only bring people good results for those who follow His path truthfully and without stumbling. It is for this reason that Rabbi Yannai checked the ferry before he entered it. He indeed took all the steps of proper precaution, without withholding any hard work that is up to a person to do to save himself from failure and stumbling.