Own It!
There is nothing wrong with having a time (moment, hour, day) of sadness. Pretending it doesn't exist can really drain you emotionally and spirirually, and can even lead to a physical ailment.
Once you acknowledge the sadness, and understand that it's ok, you can own it. Once you take ownership of this feeling you can confidently let it go so you can move on to bigger and brighter moments.
Put another way, you cannot let go of someone else's property, you can only let go of what you actually own.
Go and encourage someone today!