Course rigourness/difficulty

As someone who is transferring my junior year and currently taking classes at a CC (yes they all transfer and give me credit). I am getting nervous that the level of difficulty will be a slap in the face once I start taking higher college level courses. For reference I plan on taking my general biology’s, general chemistry’s, calculus, and other electives. I feel like all I keep hearing is “be ready to struggle” and it’s making me feel pretty discouraged like i’m not prepared enough. (I have guaranteed admission under the transfer program im under and one of the requirements is getting a B or better in certain courses i am taking here at CC.) can someone maybe give me better insight on what to expect or if anyone has been through this same feeling?