Reading source code is one of those things that I feel that nobody likes, while the advantages are so clear. You can brush up language skills, find out how other people solve things, learn different architectures, find out what the quality of a code base is, play spot-the-pattern et cetera. One cause could be that you don't learn reading other people's code in college. On the contrary, they want you to create little pieces of code that can easily be kept in one head and where correctness is easily demonstrated.
The real world doesn't work like that. If your day job isn't maintaining other people's code in the first place, then you'll get to see your colleague's code at the end of the project when they move on and you get to stay for a little while. Either way, you'll just have to accept that you don't understand everything and get on. For those people who still have that barrier, I did a little writing on how to search through code and getting it to work the way you want it, without feeling lost. We're going to look at Adjusting Starfighter.