Wow! This is a very important initiative. Kudos to Yo Yo. Always admired his ability to empathize. Here are my 2 cents.
Although I was fortunate to cross the line this year, I speak this from past experience. There will certainly be a feeling of hollowness but accept it. If toppers make tall claims, take it with a pinch (maybe, even a bucket) of salt. Preparation for this exam takes time, effort, and energy. It's not a cakewalk.
1)SELF: Do not be too harsh on yourself. This exam doesn't determine your worth.
2)DON'T BE IN ISOLATION: Talk to friends/family. Do not self-isolate. Avoid staying indoors for too long. Go out for a walk. Get some fresh air.
3)NO COMPARISONS: Refrain from comparisons as each one has a different starting point.
4)NO MAJOR DECISIONS: Do not take any major decisions in haste. More often than not, you may not have thought through it properly.
5)GAIN PERSPECTIVE: Many others are in a far worse situation (our migrant workers during the lockdown, refugees in West Asia, victims of the Beirut blast, families affected by the pandemic, etc.). You are in a much better situation.
6)PRACTICE GRATITUDE: Be thankful for the smallest of things. Are you in good health? Are you able to eat 3 square meals a day? Do you have a roof to stay under? Do you have a family? Do you have access to electricity, clean water supply, internet etc.? Well, count yourselves lucky! Many others don't! Also, treat this as a welcome break because you also get more time to spend with your family. Tomorrow when you get selected, you won't have this luxury.
7)BOOKS AND MOVIES: Read good books (Viktor Frankl's story, Sapiens, Guns Germs & Steel etc.) and watch inspirational movies (Shawshank Redemption, Forrest Gump, Good Will Hunting, October Sky, M S Dhoni etc.). Some examples I could think of. Others may add more.
8)EXERCISE: Exercise regularly at least for 30 mins/day (Nike Training app is excellent; do burpees, squats, push-ups etc.). Include meditation too (10 mins mindfulness meditation on YouTube serves the purpose. There are apps too).
9)THINK BEYOND THE EXAM: Tomorrow, you will face bigger challenges as a civil servant. Whatever you are going through is only making you stronger and more resilient.
10)MOVING ON: Even if you have decided to move on, don't have any guilt or regrets. You have given your best. In an exam where there is enormous competition, luck also plays a part. Your energies can be put to better use elsewhere. There are so many opportunities awaiting you. Just look around. If anything, preparation for this exam has given you greater exposure. You can take decisions more wisely.
Good luck! We are unique and special. And we have to truly believe that. This will transform our mindset. Life will surely reward us. It's only a matter of time. 
PS: For those giving Prelims, it's around 50 days away. Nice way to forget everything and focus all the energy there.
