Reassurance isn’t reassuring after awhile?

Hello! I just got diagnosed with OCD a week ago and joined the app today to find a sense of community. Since my understanding of treatment is minimal at this point, I'm confused why everything on here tells us not to seek or give reassurance? If someone could explain the reasoning behind that it would be greatly appreciated, as I want to make sure I'm not only watching out for it in my personal life but also using this app appropriately.

When I was a child, before I knew this was OCD, I struggled with constant "magical thinking" compulsions (don't step on the crack or mom's back will actually break, etc). When I later learned this was OCD, it almost immediately solved it. Any time I got a magical thought, I would say to myself "that's just an OCD thought. ignore it." and it just stopped coming! Like seriously it fixed the magical thinking stuff forever. But of course the OCD has resurfaced in other ways. So naturally, I've tried to use the same strategy since I had so much success with it previously. But I wonder sometimes if telling myself "that's just OCD" is almost functioning as a reassurance compulsion? I hate how meta this gets. For example, I have ROCD that comes and goes. So sometimes I'll get a thought like "what if i'm still in love with my ex?" and then I'll tell myself "that's obviously just an ROCD thought" and will feel relief, almost like reassurance. But it comes back. So is telling myself that it's OCD a reassurance compulsion ?? It's just so weird because it worked so perfectly as a kid with the magical thinking thing.

Does anyone else experience a moment of clarity where you feel strong relief that the intrusive thought isn’t true, only to then immediately start questioning if you’ve only convinced yourself that because you don’t want the thought to be true? I’m pretty confident it would take some crazy mental gymnastics to actually successfully convince myself I didn’t do something that I deep down knew I did, but every time I resist the compulsions and try to sit with the uncertainty or tell myself to think about what is logical, I usually briefly know that this probably didn’t happen but am unable to move on out of fear I’m just in denial and have convinced myself of that.