A psychiatrist offered this analogy:
Your brain is like a computer which has a fixed amount of memory.
When your brain is occupied trying to process depression there’s a fixed amount available to use to process other activities, say memory or long division. Eventually, as you heal, more memory is made available to concentration or routines or interest in life or, in my case, facing the ashen landscape called life to which a debilitating, manic, and, calamitous event crippled my job, my family, and my spouse.
- This Is How Your Brain Works (mashable.com)