According to Goethe, the only people who are truly happy are those who are like children, who are made blissful by the smallest things, and if you try to see life as it is you would be doomed to despair. What would fulfill the requirements of being like children, and how would that make you happy?

The image of the happy child is often invoked as a model for adult happiness (you mention Goethe; Nietzsche, in Thus Spoke Zarathustra , in the section on the three metamorphoses, for instance, does so as well). While this seems an overly romantic view of a child's world, the model as such has at least the following components: 1. Children, it is said, lack a complex inner life, so that their responses to events are immediate, near-instinctive, and without the quality of angst that can often accompany adult retrospective analyses of actions taken, nor the having of second thoughts about the wisdom of having taken such actions. There is a kind of freedom that an adult could well experience in virtue of being able to act to a situation by assessing it swiftly and with clarity at the outset, without the conscious intervention of a range of beliefs and desires that typically precede (and stultify?) adult action. 2. Connected to the first component, children lack the baggage of the past, and...

Is every type of happiness or pleasure explainable (possible to articulate through reason or logic)? Should I be distraught that I am unable to articulate clearly some of my pleasures? And does an unexplainable pleasure (if it exists) suffer from its unexplainable nature or flourish because of it?

Approaching your question a little differently, one might ask a further, pragmatic question, to wit: what difference does it make in your life (to your happiness, to your sense of well being, to your life projects) to experience pleasures/passions that remain inarticulate or not fully articulable? If the inability to symbolize a passion, or to capture it in a string of sentences causes you a measure of suffering, then it makes sense to attempt an articulation of it or to ask why that matters to you (therapists -- of the psychoanalytic persuasion, among others --make their money engaging in just this form of labor!) On this more pragmatic approach, the issue would be less whether one "ought" to be more clearly representing ones pleasures to oneself in order to experience them more completely (in some sense), as an embodiment of the maximally good life, but rather whether the existence of specific non-fully articulable pleasures/passions seemed to you (or to you in relationship) to be preventing you...