Write it DOWN!
When you complete an assignment save it in your own files before you submit it, when you talk to someone via email save every email correspondence, and even when you talk to people in person sometimes follow it up with an email that starts "per our conversation..."
Be a Leader
Boss, owner, CEO, supervisor, director, all titles for the person with the power. Be a LEADER instead; a person that inspires and motivates those around them to be their best and do wonderful things by being a honest, humble, respectful, responsible, positive, creative/forward thinking, encouraging, confident, communicatior.
One way to manage a large task is to break it down into smaller tasks and once one of those smaller tasks is completed treat yourself to a snack, walk, or even a few minutes of mindless browsing on the internet.