Eh, it can be quite painful, but you just need to reach the point where bullying someone else is less of a hassle.
Kind of a late reply on this one, but I’ll point out that this depends on what kind of bully you’re dealing with. Not all bullies are opportunists or cowards, and in particular some are playing a dominance game which they will not permit themselves to lose. To respond to a challenge by changing targets would be to implicitly acknowledge that they don’t have dominance over their original target, something they’re unwilling to accept, so they’ll respond to challenges by escalating until one side is unable to keep up. This is the kind of case where getting outside intervention is usually the most necessary.
Kind of a late reply on this one, but I’ll point out that this depends on what kind of bully you’re dealing with. Not all bullies are opportunists or cowards, and in particular some are playing a dominance game which they will not permit themselves to lose. To respond to a challenge by changing targets would be to implicitly acknowledge that they don’t have dominance over their original target, something they’re unwilling to accept, so they’ll respond to challenges by escalating until one side is unable to keep up. This is the kind of case where getting outside intervention is usually the most necessary.