Ad set profitable for 3 days, then losing money.

When an ad set is super profitable for 3 days and then starts to drop, what should I take away from that? I'm trying not to panic, but it's still frustrating. This is an issue I also had on TikTok, which is why I switched to Facebook, but it's the same thing here. A ROAS of 2.5–3 for 2–3 days, then a total decline.

Are your winning ads consistently profitable every single day? Please, I’d really like to understand the reason and figure out what I need to reevaluate.