Some people find that whomever they date, they invariably find themselves dissatisfied. Nothing seems to work for them.
Usually, people who struggle in this way think they are being entirely reasonable and are entirely unaware there could be a problem in how they view things. A common cause is that the person has “a divided self,” in which they have quite irreconcilable “parts” of their character that want and need different things and are pulling in opposing directions. The person’s divergent instincts are never going to agree on who would be a suitable marriage partner, given their dramatically different expectations. This can easily result in dating paralysis.
Whoever you date, one part of you will be deeply unhappy. Finding someone who will satisfy both sides of your character is nearly impossible, given your internal conflict. This has nothing to do with mental illness, but the impact on dating can be significant all the same.
For people like this, deciding to marry someone can be a truly traumatic experience. It is not something that you are likely to achieve without proper advice and support.