A short background. I learned with Rabbi Singer for 7 years. He was my mesader Keddushin (and my brothers as well). The last time we spoke was a year ago.
The first story is about my friend. This story took place back in the 90's when Rabbi Singer was giving shiur either in his house or in the shiur room in the Yeshiva Gedola. He was persistent and always trying to encourage people to learn. Some came eagerly and regularly, sometimes it took a lot of effort and encouragement. One of the latter was a friend of mine. He came once or twice and after that Rabbi Singer encouraged him and prodded. He reminded my to talk to him and encourage him. But it did not seem to be working. At one point I wondered it my influence was having any effect and I asked Rabbi Singer "should I keep asking him?" I don't think I will ever forget his response, delivered with complete conviction (devarim hayotze min halev) "YOU NEVER GIVE UP ON A JEW" Wow that is a klal that has stuck with me and has been a guide for me many, many times.