You can lie to your neighbour or a member of your family. You can hide your feelings from the closest of your friends. But, for your own sake, stay true to yourself!
Knowing exactly how you feel is really the first step towards feeling better. If we are happy all day long and, suddenly, we become sad, we should know exactly what went wrong.
Knowing exactly what is wrong is a relatively hard thing to do. But you become closer to an actual solution because you would know how to create and assess your own version.