For years, I played for a few months intensively and then lost interest.. This happened again and again over the years. I did almost everything to keep myself motivated and keep playing without any success. I got books and tried to read them, got a nice board to motivate myself. Downloaded pro games and replayed a few. Joined the go local club and tried to attend go evenings as much as I can to no avail.. Don't get me wrong, I'm not aiming to become a pro or have any ambitions becoming better etc.. I love the game, just the game, in a degree that I didn't completely stop playing over the years nor I was able to keep myself motivated to play regularly..
Discovering OGS was the first step to true motivation for me honestly. OGS has a lot of different aspects which might keep you motivated. Problems, professional games, groups, ladders, tournaments, joseki library. A huge resource.. For me it was the correspondence games.. As the life gets quicker and the free time scarce, correspondence games fits perfect to the scenario and fills the void for people like me. I can play my games without the pressure of time, one move at a time.. You gotta be careful tho, it is very different then playing a normal game and if you play only correspondence games, your ranking will not reflect your true ability. After playing only correspondence games for a long time, I attended a go tournament and was unable to win against those lower ranked then me..
I guess balance is the answer here like everywhere else. Correspondence games will keep you motivated and help you improve but if you wanna reflect your true rank, better keep the balance and play normal games every once in a while..