"Ignore" means "to refuse to notice" and so is not a synonym of "succumb." "Yield," "relent," and "defer," however, all mean to give way to someone or something that you can no longer resist. Use "yield" to mean a giving in to force, argument, persuasion, or entreaty, as in "yields too easily in any argument." Choose "relent" to imply a yielding through pity or mercy by someone who holds the upper hand, as for example, "finally relented and let the children stay up." And try "defer" to imply a voluntary yielding or submitting out of respect for or deference toward another, as in "deferred to her expertise."