Out with it!
It might be a harsh way of framing the thought but its the most straight-forward way I can think of.
A more polite version would be: "Express Yourself"
I for one belong to the category who has to learn not to express everything but somehow thats one lesson which continues to evade me on purpose 
A lot of people however,Iv noticed dont feel that comfortable about speaking whats on their mind, as it is. I know the people Im talking about are confident. So the matter of self-doubt doesnt arise. Then why dont they express themselves? I've asked them the same question and all i have for an answer is that they just cant.
I dont know the reason but if I knew, Im sure we could work something out and get them to be more expressive.For one, I know its a lil difficult to deal with clamps who clamour everything and hold it close to their heart, never letting anyone know anything. Opening up is filled with positives that any negative one could think of is easily negated.
It makes a lot of difference when one expresses themselves. For one, theres not much ground for doubt/suspicion, it gets people close to you, warms up relationships and just gives a special glow 
Then why hesitate? I'll give you one more reason not to hesitate- nor you nor i have any idea about whats going to happen next, so why not live for the moment?! Tell those you cherish that you cherish them, those you dislike..hmm..maybe that we could put on hold
Come on, open up and be out with it!!
Truly agree with the theory of "Out with it!"
I too believe in it. Venting out helps a lot! And being expressive makes things simple.
Nice post.