Hi and welcome! I'm a little late to the party but thought I'd weigh in briefly.
I agree with Paulski. Because your song has what is called an unstable theme. Some elements that support unstable themes include near rhymes, irregular rhythms, and uneven numbers of lines. You do have some irregular rhythms, but you lost your near rhyme element when you changed to all perfect rhymes. I would seriously consider taking the best of both your old and new versions to see what you can put together.
I also suggest watching for too many repetitions--like your five uses of the word "now". Perhaps some could be left out or changed to something else? Also, the word "just" occurs three times, I think. Maybe something else would work instead of one or two of those, especially one of the two that are close together. Here's an example of something you could do in one spot:
Though Our love just quickly faded and we drifted fell apart
You will always own a piece of my heart
By the way, all these comments relate to your revised version, not the original.
This kind of love lost theme is popular, so I think your song has potential, and I encourage you to keep working on it. However, don't get yourself too frustrated. You say this is your first attempt, so my recommendation is to get it to a point that you think is as good as it's going to get, at least for now. Then choose a new theme or topic and start another one. The more you write, the better you will get.
I also recommend checking out posts from other members...see what you like and don't like about their songs and let them know. It isn't necessary to be an expert. Leaving some comments will help you gain some understanding about writing and you'll have the added bonus of getting on the good side of anyone you give feedback to which just might make them more likely to leave you some feedback, which will again be helpful (hopefully) to your writing.
Good luck!
Vicki