The weight gain freakout is something I experienced many times before it became low-drama. I was used to the scale having meaning. It had powerful control over my mood and behavior, but only because I'd given it that, not knowing any better. Once I began weighing on a regular basis, I realized just how much the scale fluctuated for silly reasons. Canned soup. Steak. Humidity. Medication. Workouts. Each new thing that caused a scale swing was so dramatic! Until I watched it right itself hundreds of times without any intervention on my part. If I do what I usually do, I weigh what I usually weigh. Anything that looks otherwise is a temporary anomaly and not a major concern. I didn't know that though until I experienced it. Maintenance was brand new. New things take practice. The mindset of maintenance takes practice. If something feels surprising or upsetting, see how it looks in three weeks. Deal in weeks and months, not single readings.
Even the momentary scheming and doubting is great because it allows you to step back decide whether that's the way you want to handle it next time. Should I freakout? Or should I see how this reading looks in a few days/weeks? Or should I even get on the scale? You get to choose. Every choice will help you in some way, whether it's a positive experience or a reminder of what you don't want. It's all part of the process. It doesn't mean you're failing or backsliding. It's what trust-building feels like, a bit messy and awkward.