Garp is stabbed:
- He says it was nothing to instill confidence in Coby and the other marines.
Do you expect Garp to fall into despair after being stabbed? How would the morale of the soldiers he commands be affected? It would plummet in the blink of an eye. That's why using the strategy of claiming that the attack was "nothing" is the best option. However, it doesn't change the fact that the attack took a significant toll on Garp's endurance.
Whitebeard also told Marco that he didn't need medical equipment, and the result was what we saw in Marineford, him being stabbed by Squard. Rayleigh is the wisest old man among Garp and WB; at least he knows his limits, the others are in denial. LOL