In the first scene in which we meet Hamlet we find out that he is still wearing his mourning clothes of black and that "the clouds [of mourning] still hang on [him]." Gertrude and Claudius both try to talk to Hamlet about his continued grieving for his recently deceased father, but they are likely disturbed by his grieving because they are clearly over their grieving of brother/husband, evidenced by the fact that they have recently married each other!
Gertrude tells Hamlet that he should move on because "thou know'st 'tis common, all that lives must die, / passing through nature to eternity." That everything eventually dies is certainly true, but that doesn't lesson the emotion of the loss.
Claudius is even more harsh in his commentary. He tells Hamlet while everyone has a "obligation" to mourn, "but to persevere / in obstinate condolement is a course / of impious stubbornness." This suggests that Hamlet's mourning is being done "on purpose" and that it is an unholy act to carry on in his grief. He makes a further slam when he adds that it is "unmanly grief." Calling Hamlet's manhood (vs childishness) into question is a rather low blow. After this comments he tells Hamlet that people who mourn to long display "a will most incorrect to heaven, / a heart unfortified, a mind impatient, an understanding simple and unschooled." There is no part of Hamlet's character that isn't attacked in that statement. Hamlet is charged with being sinful, weak-hearted, impatient, and stupid! Claudius touches on the same theme as Gertrude when he points out that all father's die and that Hamlet needs to get over it and accept that he will next on the throne after Claudius and that he should just move on.
We don't know a lot about Hamlet at this point in the play, but this speech makes us very disturbed by Claudius and makes us feel more sorry for Hamlet than we did before this scene. Neither of the adults seem to be very sympathetic at this point in the play.