Consider this sentence:

They may also be reticent about sharing bad news with you.

Are they reticent? Or are they reluctant? It's a subtle difference to be sure. But is it worth preserving?

Reluctant means resisting, unwilling. There's a strong negative connotation attached to it, as these examples demonstrate:

The US healthcare industry has been extremely reluctant to embrace outsourcing firms.

The subject lends itself to hyperbole both because of its urgency and the imperative to draw reluctant readers.

US websites are reluctant to remove extremist religious material because of the First Amendment to the constitution protecting free speech.

By comparison, reticent means quiet, restrained, unwilling to communicate. Despite the unwillingness component, reticent imparts less of a negative feeling:

They were reticent about their main concerns, and few wanted to talk about how they voted.

The mustache and beard deny us the opportunity to get too close to the man, whose reticent gaze appears fixed to the floor.

Korchagin, usually calm and reticent, spoke with a passion that surprised Tsvetayev

Garner's Modern American Usage reports that reticent for reluctant is at stage 4 of language change: a nearly universal form that only "linguistic stalwarts," those "die-hard snoots," object to. Those snoots (syntax nudniks [pests] of our time) are people who love language, are at ease with its nuances, and tend toward tradition, rejecting neologisms without good cause.

It's up to you, then. If you're in favor of preserving the nuance between reluctant and reticent, then be proud to be a snoot!