It feels good when the day before, the job I was worried would be difficult to do actually got done easier than I expected!
ご質問ありがとうございます。
"It feels good when the day before,"=「前日、~のときはいい気分だ、」
"the job I was worried would be difficult to do "=「やる仕事が難しいのではないかと心配していたのが」
"actually got done easier than I expected!"=「実は思ったより楽に出来たとき!」
ご参考までに。