那些不注意爱惜自己的人总有一天会懂得保护健康的重要性。（come)

Those who do not take care of themselves will come to value health eventually.

To upstairs: a grammar error
keeping healthy
not keep healthy

and your use of the phrase "come up with" is, frankly speaking, quite chinglish

those who didn't care about themselves will come up with the importance of keep healthy.
come up with 想到，懂得

come用在“会懂得”的“会” 的翻译上
The people who don't cherish themselves will someday come to realise the importance of protecting their health.