I am personally a huge believer in this mantra and say it all the time. I find it incredibly reassuring to know that, at some point, the reason will be clear. It’s far from toxic, IMO. Only one of my kids was a little disappointed with her college results, and in fact, it ended up being great for her.
The “reason” she didn’t get in to her top choice is more clear to her as she gets older. In fact, she ended up in a grad school program at a place she viewed as a thousand times better than the top choice back in the day. Had the top choice happened, maybe her path would have been different. It’s impossible to know. But at least for her, my daughter found it helpful to think that she would eventually know there was a reason she didn’t get in: that school wasn’t meant to guide her on her path.