Miss Maudie tells Jem that things are never as bad as they seem. What reasons does she give for this view?

Jem Finch and Miss Maudie are characters in Harper Lee's Pulitzer Prize-winning 1960 novel To Kill a Mockingbird.
Chapter 22 of To Kill a Mockingbird begins with Jem weeping as the all-white jury convicts Tom Robinson of the rape of Mayella Ewell, despite there being little or no evidence that he committed the crime. As the Finch family attempts to return to their life of relative normalcy after the trial, they are exhausted by the subtle aggression of their white peers and the gossip that follows them around. After a particularly annoying confrontation with Miss Stephanie Crawford, wherein she quizzes Jem about the propriety of his being present at the trial, Miss Maudie invites Jem and Scout to her house to attempt to cheer them up. Here she gives them some cake and says to Jem

"Don't fret, Jem. Things are never as bad as they seem." (Chapter 22)

She says this in the context of Jem being disillusioned with the people at Maycomb, who he previously thought were the "best folks in the world" (chapter 22). He does not think so now, because of their display of racism at the trial.
Miss Maudie gives him the following reasons to be hopeful:
There are people in the town who are good-hearted and attempt to help Tom Robinson. These include the African American community, people like Miss Maudie and the Finches (who are whites who believe in equality), Mr. Heck Tate (the sheriff who attempts to protect Robinson), and Judge Taylor (who appoints Atticus to the case despite the Court-appointed defenses going to Maxwell Green, the newest lawyer on the court, because the judge wants Tom to have a fair trial).
The jury deliberated on the verdict for a long time. Atticus got them thinking, and it shows that the people of Maycomb still recognize justice and that one or two of them would be adamant enough to insist on Tom's innocence. Miss Maudie calls this a "baby-step" (chapter 22) and encourages Jem to consider that this means change may be coming soon.
People like Atticus Finch exist and do their Christian duty, which transcends race to uphold justice. Their presence means that change may slowly come.