I rely on a friend to motivate me into completing assignments.. or new guns that have good stats. I'm all about efficiency when it comes to FPS, so I tend to find something that works well and just stick with it. It happens in life as well (especially with cooking meals).
I should start playing BF4 again actually. Titanfall really isn't as fun as what I had expected. The speed and chaotic nature of it means I can't really predict what will result from my actions. I can't execute wall-runs with exact accuracy, so half the time I run up the wall or jump at a ledge not knowing whether I'll make it up there or not. In general it's a whole lot off "I'll do this and see where it gets me", which doesn't feel rewarding. I also don't play defensively or smart enough to make Titans useful. I pretty much call it in to run around while I try killing other pilots.