Our Gemara on Amud Beis discusses an important psychological and halakhic principle: 

נמצא אתה מכשילן לעתיד לבא

If you take a certain action now, you will cause them to stumble in the future. This reasoning applied to the case of the 40 pairs of witnesses who came to testify about sighting the new Moon. Even though technically we allow them to violate the techum boundary for this mitzvah, Rabbi Akiva detained them since clearly they had more than enough witnesses. However, Rabban Gamliel authorized them to come anyhow. His reasoning was: “If you detain the many people who wish to testify about the new moon, you will cause them to stumble in the future. They will say: Why should we go, seeing that our testimony is unnecessary? At some point they will be needed, and no witnesses will come to the court.”

This principle, that we allow an action that is not strictly necessary in order to avoid discouraging people in the future, is used in other areas of Halakha. Most notably, it is part of the heter that allows Hatzalah and other emergency personnel to return from an emergency. That is, if they weren’t permitted to return, it might affect recruitment in the future. (There are nuanced discussions in poskim about how and when this heter applies, as it may be subject to certain conditions such as the act of return still remotely being possibly part of the mitzvah by being ready for the next emergency and/or the expectation of return being present at the outset. Consider a doctor who left for what was supposed to be a 12 hour surgery that would end after shabbos. If the surgery ended quicker than planned, he might not be allowed to return. As it would not have been within his expectations to do so in the first place had it been a weekday, there is no discouragement for a future scenario. See שו״ת חתם סופר או״ח ר״ג, אגרות משה ח״מ ב:עט:ג או״ח ד:פ )

While on this topic, I was involved in a situation with a Dayyan who meant well, but was not particularly psychologically minded. He sort of got why therapists don’t try to be mekarev clients.  He understood that the neutral environment of therapy allows people to express themselves more freely, and also make healthier observations and decisions about themselves when they are not burdened with the pressure to comply or please others. Still, he was upset with me that, after all said and done and I established a trusting relationship with the client, why didn’t I join him in sharing my condemnation of what the client was doing, which was “clearly wrong”? Fortunately, I was able to cite this principle as proof for my position. Even if in this one case I would be able to use the power of our trusting relationship to convince the client to do the right thing, this would still ruin the trust of therapy in me or maybe other therapists in the long term. נמצא אתה מכשילן לעתיד לבא!

Another example is regarding a child who has some dangerous or shameful secret that he or she wants to disclose, such as if they are being inappropriately touched or maybe a friend is in some kind of trouble. A teacher or parent may wish to offer reassurance such as, “You can tell me anything. I promise to keep it a secret. I won’t punish you.” However, this is wrong and dishonest. The fact is, depending on the situation, a parent or authority will need to react or respond, tell others and / or enact consequences. You simply cannot promise such things. 

So, what do you say if the child says, “I will only tell you if you guarantee that you’ll keep it a secret or you won’t get mad.”? You must be honest, compassionate and firm. You can say something like, “I treat your privacy and your choice to tell me with respect. I cannot promise what I’ll do but I can do my best to respect your privacy while also your safety, and the safety of others. It’s scary to share a private or secret matter but it also can feel good to get it off your chest. Sometimes when you talk to someone else, things that seem impossible or very embarrassing, start to feel better.”

You might say, but what if that doesn’t work?  People don’t always work or do what we want, especially children.  That does not mean it is wise to lie or mislead in order to get what we want or think is right.