For many students Algebra 2 will be one of the most challenging classes of their high school career; especially second semester where the bulk of the new concepts lie for most textbook aligned courses. Start this grading period by flipping through the remainder of your math book and asking yourself these questions:
How many concepts do I recognize?
How many topics are completely new to me?
How does the ratio of "recognized : completely new" compare with the material you covered first semester?
If there is a big difference between the two then be proactive about how to adjust your approach instead of being caught in a panic six weeks from now. Plan more time for homework, start or join a study group with classmates, ask your teacher about online resources for your textbook series, and/or do a little research on local tutors.