ものだ

「ものだ」expresses:
1. Something the speaker considers natural, obvious, or the inherent nature of the object, the situation.
2. Something that the speaker considers customary, the right way to behave in general... should be done, thereby indirectly advising, gently warning the listener. Note: The subject in the sentence should not specifically target the listener but rather speak in a general sense to everyone. Not used with superiors.