Not sure about you, but I made yearly goals from the start that motivated me to stick with it daily. Year one (June, 2013 to June, 2014) was all gold badges. Took 4 copies and a crazy amount of time, but I did it.
Year 2 was just as difficult, grow every type of hybrid on my own! Then, arrange them into patterns throughout the town, putting all colors together and all types together. That was unfortunately not made technically, as I ran out of time, so I had to start using some secondary towns to grow those buggers! By the way, there ARE hybrid red pansies and roses that yield the purple pansy and blue rose, I followed it using an insane growing method in the Japanese guide, but it worked, I got every flower type legitimately on my own.
The third that I'm in now involves my other copies, but I'm trying to incorporate more people, and that's reach a certain number of dreamers and visitors. I can visit myself everyday with the other towns, and by breaking it up, it kind of forces me to play everyday to make that goal- I'm ahead of pace for the visitors, but not the dreamers, so I may need to dream my own town, but I don't like doing that.
What I thought about for year 4 is having a 100% catalog, which I know involves trading with someone who uses cheating devices, because that one shirt hasn't been released, and likely never will be. After year 4 though, I honestly don't know how much more I can aim for, everything will be done, on top of the ultimate goal- keep all 10 villagers that I've had since October, 2013. So far, that's been easy, don't stop until all outside villagers run up and talk to me, just to make sure none says "yo, I'm moving, so bye"- "uh, no, you've been here 50 years, you're not going anywhere buddy!" LOL
That's about all I plan to do, play it daily for 4 straight years, but Wild World got daily play for 5 years, so maybe I'll think of a good year 5 goal at some point this coming year. Anyway, that's how I never stopped these years, hopefully you can find something that keeps you in it too.