Reddit mentions of First Course in Mathematical Logic (Dover Books on Mathematics)

> Unfortunately, since that last class, I've fallen out of it and I'm not entirely sure how to get back in. I'm not very good at teaching myself things.

I think that self-studying is a skill. And just like any other skill, you become better at it the more and the better you practice it. If you aren't very good at it yet, then you probably just haven't done it much, or perhaps you haven't done it properly.

If you don't know where to start developing the skill, I highly recommend reading the article The Making of an Expert (PDF) by K. Anders Ericsson, published in the Harvard Business Review. It is a concise introduction to Ericsson's research on acquiring expertise, full of valuable insights. Some of the more useful and relevant ones are the importance of deliberate practice in acquiring expertise, how long it actually takes to become proficient in a field of expertise, and the fact that the final stage in acquiring expertise involves no instructors (i.e. it is characterized by self-studying).

I also believe How to Read a Book by Mortimer J. Adler to be useful in developing this skill. This book describes the difference between present teachers, like the ones you can interact with in an educational institution, and absent ones, such as the authors of books. It then lists a number of very useful general guidelines on how to approach learning from these absent teachers, followed by some more specific ones describing how to approach different kinds of reading matters. It is essentially a self-studying guide.

And since this is /r/logic and you expressed an interest in getting back into the subject, my final recommendation is A First Course in Mathematical Logic by Patrick Suppes and Shirley Hill, which is an exceedingly lucid, accessible, elementary and rigorous introduction to logic. It is very well-suited for self-studying and might be a useful refresher, although depending on the courses you've taken and how much you recall from them, it may be too elementary for you. I posted a more detailed description of the book in a different thread on here a few days ago.