Using the solutions manual can help:
The by David J. Griffiths is a staple textbook for undergraduate and graduate physics students. A comprehensive Instructor's Solution Manual Using the solutions manual can help: The by David J
7.1 The weak interaction is responsible for $\beta$ decay. Using the solutions manual can help: The by David J
The problem sets at the end of each chapter are not simple plug-and-chug. Griffiths asks you to "fill in the missing steps." For example, a typical problem might state: "Starting from the Dirac equation, show that the probability current satisfies the continuity equation." The gap between the starting line and the finish line can be 10 lines of algebra involving adjoint spinors. Using the solutions manual can help: The by David J
Spend at least 30 to 60 minutes struggling with a problem before looking at the solution. The growth happens in the struggle.