The thing that I find when I'm animating, is how fast you can go from knowing where you want to go to five minutes later getting completely and utterly lost in you're animation.
Then you're stuck and you can't go forwards or backwards because you might of lost part of your "really, really awesome" blocking but you have in turn made some "really sweet" poses or keys later along the time line.
Firstly did you do your planning? is there anything to fall back on when your stuck, lost and alone in the middle of your animation. Video reference? did you take it more than once so if a pose doesn't work you have more of an idea how you can lay out other poses. How did your character dialogue sound? have you written out what you thought the character was feeling through their dialogue. Expressing thoughts by thumbnails, writing out or expressing the major beats in timing on pieces of paper. This is your map, take care of it this will be the decider between whether you will be able to get to your destination on time or you will be in a highly stressed, fully caffeinated state and crying in front of the computer while your deadline starts being a thing of the past and you really have to work to catch up.
Thirdly, Believe in yourself. You are the animator, you are the master and commander of the scene. Sure you might be doing the animation for someone else but unless you have the producer/director sitting there animating your scene, it is your own to express. You are always going to feel like you can make it better, everyone does. But it is up to you to take your mistakes and learn from them. Don't be scared of getting lost if you know that you can get out, then it can be quite exhilarating to understand and experiment with your map. That's how you get better, understanding why you did it in the first place and how to avoid it next time your animating. Even better is if you can learn from other peoples mistakes as well as your own. Don't be afraid to ask questions and learn more about "humanity" the one animal as animators we are always trying to imitate.