I think it makes sense for you to withdraw if you believe you'll get a C. While multiple Ws aren't great, if you're planning on doing a masters, some research, etc before applying to grad school those factors should outweigh those 2 courses, particularly since they're not related to psychology. If you continue to keep your GPA in the 3.8 range, do well on the GRE, and get a good amount of research experience, you should be okay. If you don't withdraw, a 3.75 is still a good GPA. Either way, you're not going to ruin your chances.