You never know what someone is going through. Be kind always. Meaning. Everyone has a struggle or difficulties they are going through, therefore, be kind, compassionate, and respectful towards them as this could either make or mar their day.
Everyone in the world has a problem they are struggling with, and the best way you can help is by being kind to them. Just because they don't talk about their situation does not mean they don't have any. People try to cover their pains and sufferings with smiles and laughter, but there is turmoil in their hearts. You not being kind to them could implicate matters. Your action could either make matters worse or maybe make their day. Irrespective of whom you meet, it could be family, friends, and even strangers; try to be kind to them. Being kind does not cost you anything.
People don't like it when someone knows about their difficulties because they might think they are being a burden, or you might judge them. But then, you can make a huge difference in their life by being kind, compassionate, and respectful: this can go a long way to help them change their lives or even save them. The smallest kind gesture, even from strangers, can make someone's day.