Every beginning is difficult. I always feel the implications of this sentence when I want to understand something completely new. This something can be a mathematical concept or a piece of code (software or hardware) written by someone else or my former self.
At the beginning you have to de-construct the work of the other person. What they have built with their creativity, you have to persistently un-build with your intelligence to understand their creative process if you later want to be creative with what they’ve done.
That’s a fundamental problem with human creativity (in certain disciplines?) that you have to go through the process that others have already gone through in order to augment their achievements. Unfortunately, you cannot just continue working with the knowledge of the other person that has been there before. There is no magical transfer of state of mind. All you can do is absorb what they’ve done and get into another, similar state of mind that allows you to reproduce and the surpass their results.
And sometimes that just feels hard. But it feels even harder if you allow yourself or other people to put time pressure on your project. This process is never fast and predictable and you never know how long it will take you to understand the creation of other people.