It’s generally considered best practice to never reuse pseudonyms.
This requires generating a new public and private key pair for every transaction you make.
You want to do this so that it’s more difficult to determine how much bitcoin you own, and what you’ve been spending that bitcoin on.
Also, imagine if you didn’t generate a new public and private key pair for every transaction, and you had all your funds associated with one identity.
As soon as you lose the corresponding private key, all your funds are gone.
It’s best practice to spread out your funds across multiple identities.
After all your private keys are just random numbers — there’s no relation between them — so compromising one key is independent of the others.
And public and private keys are computationally easy to generate anyways, so why wouldn’t you generate new public and private keys for every transaction? It’s a little effort that could potentially go along way in saving your Bitcoin user experience.
Wallet software will generally handle this anyways, making it so much more easy to comply with best practices.