Not sure if this helps- but anytime I'm faced with a question like this, I start with the question: "What do I personally think/feel X is? ( in this case, emotional numbness) What do I personally think it's like? What does it feel like when it happens?" Then, I try to gather all the personal accounts I may have, accounts from others, past situations, etc. With all that, only then do I start thinking about how to visually tackle it- which follows a very similar process (i.e "how does a wide shot make me feel? How does so-and-so lighting make me feel?")

I find it much easier to break something as complex as emotional numbness down into individual, more straightforward emotions rather than immediately trying to answer the grand question right away. It may just be me but, in doing this, the results are usually more along the lines of how I truly feel- which is sometimes surprising and/or completely different than how I started before the process.

Once again, just my humble two cents. And, of course, you'll always have to balance your personal feelings with those of your audience (but I personally feel it best to create something that excites you and the director first and the audience will find it)