The Bite-Sized series of articles is meant to take the most powerful cards in Dominion and give a short explanation of what makes them powerful.
Taking an extra turn in Dominon is great, and Seize the Day doesn’t restrict what you do with your extra turn in any way. This event should be bought in pretty much any game it appears in.
Usually you’ll want to Seize the Day later in the game, where $4 and a Buy is a smaller price to pay relative to whatever else is going on in your turns. If you are playing a money density deck, Seize can serve as a re-roll for a bad turn when you’re greening. If you have multiple buys per turn, Seize the Day is a huge endgame threat that vastly changes what you have to play around when your opponent hasn’t used it, and if it isn’t played around, Seize the Day just wins the game for you.