Sometimes a fall can lead to freefall. Freefall is worse than falling. It's falling fast, out of control. Like falling 3 nights in a row after a long upwards climb.
Every fighter needs to learn how to fall. Over the years I learned how to prevent a freefall, and here are my tips. Obviously what works for me may not work for you, so make sure never to fall in the first place!
1) After a fall, it's very natural to be super emotional, either sad, depressed, or angry. With all those emotions (and changed brain chemicals resulting from the fall), that's the worse time to think about your fall or what caused your fall. Just chill out and try to get through your day without self-criticism. In a few days you can analyze the fall, be self-critical, and make any additional changes/safeguards in your life. But not now. For the same reason, don't have any critical discussions with a friend/spouse/date, or make any important life decisions. After one or two nights of good sleep you'll be back to your usual self.
2) If you're feeling remorse, spend a little time on heartfelt Teshuva. And Mikva and the Tikkun Haklali, if you do that. But don't spend the whole day on Teshuva, it will drag you down emotionally even more than you already are. You'll have time for complete Teshuva another day.
3) Because you just fell, you're at your most vulnerable stage. The Yetzer Horah will try to make you fall again immediately, convincing you that your fight is hopeless, or to "get in one last cookie before the diet starts again". Tell him that you'll listen to him tomorrow, but not today. (When tomorrow arrives, you'll be feeling better and stronger. And even if you do fall tomorrow, it's still 100 times better than falling today). The Gemorah says, "If I ate Garlic and have a bad smell, should I eat more Garlic and smell for longer?".
4) Congratulate yourself on your past successes. And learning how to fall may be as valuable a skill as learning not to fall, so today you're also making progress.
5) If you're in freefall already, remember that Hashem is always with you, even in your sins. And don't forget to open your parachute!