Absolutely this!
I've done something similar. Went from running reasonably regularly a few years ago, to pretty much zero. And put on 15kg in the process. At first it's disheartening when you look back on how fast or far you used to run compared to now. But if you make the switch to 'look where I was last week/ last month' it all begins to look rosy again. It's all the fun and excitement of starting out as a runner, with the added benefit of knowing you can do it (because you've done it before)!
Get the miles in. Check you're not trying to run too fast (i.e., go for miles/ time on your feet as opposed to speed). The kg will be dropping off and the pace increasing before you know it.
I've also found that looking back through old running diaries, photos, even race results has been quite inspirational.