Stop looking so hard outward and focus on looking inward. We are all looking for a great partner but we can be less focused on being a great partner.
Respect yourself; do not get involved with someone not available, physically, or emotionally, respect yourself enough to know you deserve more. Make sure the person you meet can see their own strengths and weakness. Someone too hard on themselves will be hard to be with, as much as someone who thinks they do no wrong. The goal is to seek someone in the middle.
Know your worth. Focus on you first, then you can focus on someone else. Are you in an emotional place to invest in someone else? Take care of your physical and mental health.
Communicate your desires openly and honestly. Be vulnerable about what you are looking for early on, do not wait to try to feel them out.
If it's a maybe, go out again. The brain looks for ways to say no - it's evolutionary to protect us. Give the person a chance - unless it's an obvious NO.
Remember that the older you are to marry, the higher the likelihood you will stay together long-term. Take your time finding out about yourself and what you really want in a partner. Patience often pays off.