In the fill up, "it is difficult ____ affection on her.", I chose "showering" out of the given options. But the answer is given as "to shower".
Now I look up on net and get that we mostly use "it is difficult to do something" rather than "it is difficult doing something"
But I wonder how can we increase accuracy on such questions. Of course, one way is wide reading but that's a long term goal, but I doubt even after that one could be sure on such things. And perhaps the other way is to cram all things. But that is hardly possible given how extensive English is.
So, I wonder if there is third way where we can learn the underlying concept or rule which would hold in most cases.
After all, it is not that we always use infinitive. At times we use gerund, like "I am looking forward to seeing you" rather than "I am looking forward to see you."
So, how do we choose infinitive over gerund or vice versa?