(But I didn't.)
I succeeded, YOU succeeded, no matter what the scale says!
Just because you didn't meet your goal doesn't mean you failed this 90-day challenge. If you participated in this challenge then you succeeded, no matter what the "results" show!
For 90 days YOU were accountable to yourself for the choices you made. You were conscious of every good decision that outweighed a bad alternative AND you were conscious of each bad choice you made over the good one. You knew that every decision you made effected YOUR 90-day outcome.
Day 90 is not the end!!! You just spent 90 days developing new habits by making those decisions and knowing how they would effect your outcome. That doesn't magically stop on day 91. You will still be in the habit of thinking about the choices you are making. Keep going! This is your new path. Sometimes we choose the wrong direction, that's okay. The important part is that you get back to the right one eventually.