Unique to Yourself
When I was at CalArts the first thing the teachers had us do in animation was to inbetween some classic Disney scenes. For the least experienced of us it was a lost lesson. Those scenes really only helped me later in my studies there when I could truly understand what the animator was doing. What it did do was give you a great big boost of confidence. Because no matter how crappy your inbetweens were the scenes always looked gorgeous simply because the animator had but so much there already.
My point here is you need to make your work unique. All these master animators did that. And I can hear you now saying, "well yeah, they were the masters". Ahh but they weren't always the masters and though they did follow some masters of their own, they built new ways of creating their animation. Even though they each have specific styles to their work they approached each new character and sequence with a uniqueness that shows in the final work. To do this they got up and acted it out. They looked in the mirror. Observed their friends and families. And yes, they had their own frustrations. Most of them would admit feeling like they couldn't get something right, or the character was so boring they had a hard time thinking of some interesting way to make them act.
So if there is any cue you should take from these masters it's do you own acting and observing and bring something new to the table.