I know that feeling since I was young. I started gaming in 1989 and already after a few years I already had to constantly switch games to keep me interested. Still today i rarely can play a game through to the end, and if I do, it will be through many different sessions over a long time span.
I got 2 suggestions for you:
1. Just play the game. If finishing it starts feeling like a chore, just stop and play something else. If you want to finish the game, then just come back at another time to continue where you left off.
2. Play some old games that you know and love in between the newer titles. This can help you get better into the mood again.
Hope this little tips work for you. They certainly did for me, as I still love gaming after almost 40 years now.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454 List as Google Doc: https://docs.google.com/spreadsheets/d/1aW2hXQT1TheElVS7z-F3pP-7nbqdrDqWNTxl6JoJWBY/edit?usp=sharing
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/
Free Pc Games thread: https://gamrconnect.vgchartz.com/thread/248138/free-pc-games/1/
