Regular beard trimming is a good practice. It keeps hairs free from dead ends and gives your beard great shape. When it comes to the act of trimming your beard, it's best to do it yourself. Maybe let your barber do it from time to time if you've built up a great foundation of trust with them.
What you probably shouldn't do is get a beardless friend to trim it. Under time pressure. Excitedly. On live TV.
Jared Leto made this mistake, letting Jimmy Fallon loose on his glorious beard live on The Tonight Show, undergoing a beard hacking that we can only imagine took a fair bit of growing and grooming to set straight again.
See if you can make it through the whole video without grimacing and grabbing your own beard in fear, as if protecting it from Fallon himself. Leto was a good sport (after all the resiliant thing about beards is they grow back no matter what you do to them) but we feel like he was secretly pretty unhappy about the whole scenario.