I think that it is important to be aware of the people around you and to realize what your actions may do to that person. I think that we are now living in an age where this is no longer the norm. Being polite and considerate does not take much time and it certainly does not cost anything.
Of course people wanting to commit suicide is nothing new, but much more help is available nowadays. Being kind and considerate to people will make it more likely for them to want to seek help, for them to see that society is not as uncaring about them, that their lives do matter.
Of course this is just a small step. Society's attitude to mental suffering or illness has to change.