Kobe Bryant to Gordon Hayward: 'Be Mad. Scream. Cry.'

Kobe Bryant says Gordon Hayward needs to let his emotions run wild -- "Be sad. Be mad. Be frustrated. Scream. Cry. Sulk." -- it's all part of bouncing back from a catastrophic injury.

Of course, Kobe knows what he's talking about -- he tore his achilles during a game in 2013 (still made his free throws) -- and fought his way through rehab to get back on the court.

So, after Mamba watched the Celtics star go down hard on Tuesday ... he penned a motivational note to the NBA star with some deeply personal advice.

"Time to move on and focus on doing everything in your power to prepare for surgery, ask all the questions to be sure you understand fully the procedure so that you may visualize it in your subconscious while being operated on and better the chance of it’s success."

"It’s a long journey but if you focus on the mini milestones along the way you will find beauty in the struggle of doing simple things that prior to this injury were taken for granted."

Kobe says in the long run, Hayward will have a deeper appreciation for the simple things like "being able to stand, walk, run" and it'll motivate him to train harder.