The line from Hamlet that best describes that Hamlet is not happy is the one where he regrets not being able to suicide because it is a sin:
<em>"Oh, that this too, too sullied flesh would melt,</em>
<em>Thaw, and resolve itself into a dew,</em>
<em>Or</em><u><em> that the Everlasting had not fixed</em></u>
<u><em>His canon 'gainst self-slaughter!</em></u><em> O God, God!</em>
<u><em>How weary, stale, flat, and unprofitable</em></u>
<u><em>Seem to me all the uses of this world!"</em></u>
He is so depressed that he wants to commit suicide for this world is so horrible for him, that finds it weary, stale, flat and unprofitable.