I translate fanfiction stories from Russian into English as a hobby and I'm a bit confused about tenses. In Russian, it's normal to mix past and present tenses in generally past narration, but I remember my professor telling me that one should stick to past tense in English. And that's what I've noticed in books, but in fanfiction, I can see people using both of them like one sentence is in the past and the very next one is in the present. I know that sometimes it's logical to mix them within one sentence, I just wonder if it works the same for the whole thing.
Would it be confusing for native speakers to read a story with a frequent mixture of tenses? I assume it wouldn't if they mix them, but I want to be sure. Note that I mean an author's words, not the dialogues:
I felt something wet on my cheek. Can it be that I’m… crying? As I caught myself thinking of it, I ran my hand over the cheek.