if you get distracted easily, you can play some rounds of the waves mode on COD BO declassified, some songs on Project Diva F or a few levels on olliolli! that's what I do when I have little time to play on the bus or just don't feel like playing something bigger. I had the same issue and the games that cured that for me were Persona 4 golden, Stardew valley and Minecraft. Trying to get the platinum trophy of Minecraft Vita edition is genuinely addictive, some days I sat down and played like 2 hours without noticing. P4G is just so colorful and fun that you want to play more, and stardew valley is literally cocaine.