In just four lines, the speaker looks at a moose and a wolf and sees something she wishes she had. The animals wander freely and exist only for today. They don't carry old memories or worry about what comes next. The title, "Jealousy," tells us this is what the speaker feels: she envies them.
The contrast is in the last two lines. She is "yearning for tomorrow," as if she wants a future that feels better or different, yet she is "trapped in the illusions of yesterday." The word "trapped" is strong. It suggests she can't let go of the past, and that the past she clings to may not even be accurate, since she calls it an illusion.
The mood is quiet, wistful, and a little heavy. There is no anger here, just a calm admission of being stuck. The short, simple wording makes the confession feel honest, and the wild animals make her situation seem even more confining.