Wait, when is this taking place??

I have been reviewing my old writing, as I've previously mentioned. One issue I have noticed is that I paid absolutely no attention to the tense. As in, present tense, past tense, etc. One moment the story is taking place now, in real time. The next, it's in the past. God bless my friends and family who read it back when I was in High School. Either my story was so interesting that they were sucked in and paid no attention, or they just didn't say anything. I'm leaning towards the latter. It's really off-putting to read a story and step back and wonder what's going on. This paragraph reads like it's the past, that paragraph was in the present, but the topic hasn't changed. It's been confusing to watch movies that jump back and forth in time, sometimes even with books that do that. My story didn't even have a time-jump feature, it was just human error. I'm amazed that I picked up on such an egregious error, perhaps I am growing as a writer. You don't want to confuse your readers, and if I was so distracted by the mistakes I've seen, I'm sure you would be too.