The following are things I've identified myself, in case it's useful for anyone else. When people say X is bad for you, they're usually right. But how bad is i

The following are things I've identified myself, in case it's useful for anyone else. When people say X is bad for you, they're usually right. But how bad is it? Will it affect you 5%, 10%, 50%? When you combine many bad things, they'll gang up on you together to make your life hell. They also affect you more the older you get. Bad things: * Lack of sleep * Lack of exercise * Social media * Drinking/drugs * Interruptions * Unresolved/ongoing family/friends issues * Bad and/or irregular diet * Not doing things you like to do. The feeling you describe using the contrived SHA-512 task, is of total, utter panic and hopelessness, putting it mildly. I don't know how deep into this you are but it left unchecked it turns into a vicious cycle. Then those bad things mentioned above are more likely to knock on your door and make the problem worse in the long run. Throughout my career I've sometimes had to use pen and paper to keep track of my thoughts while reverse engineering (which you are doing) or debugging spaghetti. File/Class names with function names and simple diagrams have been very helpful. I've found out that trying to save time by not setting up a proper debugging environment is a very bad thing. Ideally you should be able to run both old server and old client on your computer. Write a very, very simple client that speaks to the old client. Add logging and breakpoints to the old API. Step through it and write notes on paper. Mental abilities declining? I don't know. I've encountered code that I struggled with at any point it my life. Perhaps the other devs know the code better or have had similar experiences. Perhaps you're working on a more difficult part of the code. I'm guessing this old API was written over a long time. As such it'll have warts and bug fixes that are not trivial to understand. Do you know the language and framework it's written in? If not, write a very simple API in that lang/framework to understand it.