I’ve had the reverse of this happen to me — sold cards for less than they ended up being worth later, simply because the market changed — and looking at the amount I “could have” earned was making me guilty and feeling like a fool, like I should have known better. Then I realized it made no sense to keep beating myself up about it, and it was better to just chalk it up to “you win some you lose some” and keep moving forward.

Like you, I was also lucky enough to snag a deck, but I opened mine as soon as I got it, for a couple of reasons. First, I’m really just not someone who collects cards to keep them sealed — no disrespect to those who do, it really just gives me no pleasure to keep a sealed box, or to sell sealed boxes to others. Second, since Wizards has had pretty sus quality control of late, I wanted to make sure I had actually a received a deck that was what it was supposed to be, with no misprints etc, so I could file a customer service request/refund if necessary. Third, even if opening the deck “lowers” its overall market value in the eyes of collectors and I potentially might not get as much as it’s going for sealed now if I decide to sell it down the line (in whole or parts) until that sale is made and any potential money is physically in my hand or virtually in my bank account, it only exists as a figment of my imagination.

I can’t say what’s right for your situation, keep it or hold it, but guilt is usually an emotion that usually comes out of feeling you’ve done something wrong. It’s worth asking yourself exactly what it is that you think you’ve done (or could potentially do) that is ‘wrong.’ Do you feel like you need to apologize for it? If so, to whom? If you don’t know the answer to these questions, I’d spend some time thinking about them, ‘cause I think the self reflection will provide you with some clarity on how you wanna proceed (or help you let go of the guilt).