Nasiha for the unmarried.
One of the issues that usually cause a problem after marriage is hiding secrets related to health. No doubt illness is a test from Allah. But it is part of the amanah of marriage to disclose any health concerns to your partner before tieing the knots. Most people hide it until they are married then things started to come out. Note that some sicknesses could be contracted either sexually or physically. So it is not fair to hide sickness. Especially sickness involving jinn. Many people are possessed by jinn, and curing jinn is a serious issue. So allow your partner to decide whether he or she wants to take the risk. But don't hide it until marriage is done.
We read from Seerah that the Prophet PBUH married a woman with an alignment. After He had discovered the ailment, the Prophet divorced her even without touching her. This proves that partners can separate if one of them hide his or her alignment or sickness or deformity. It is also one of the duties of the guardian to mention any health concerns during the first meeting. So that the couple can decide for themselves. This brings me to another discussion. It is permission for a man to ask his intended to display herself without Hijab (But not naked). The hadith is narrated in Musnad Ahmad, Abu Dawood, Hakim.
Note that seeing her is not disrespect towards her. Remember marriage is a lifetime commitment. Many marriages have ended because the partners made the wrong choice. Many people have what they desire in their partner. For example, some want slim partner, some want plumpy parter, some want big front etc.