Planning to get married is great. You are worried you are not finding the right partner.
What are your expectations from a partner? You need to identify these. For example, are you looking for a career person, in the same sector as you? If so, will you support her with managing the house? You have listed you are a very supportive person. Kudos!
Make a list of your expectations. When you find someone who meets some of them, maybe you can take the next step.
However, is the person right for you, who can tell? Only after a few years together, probably you can arrive at some conclusion. Instead could you list out what you bring to the relationship?
The appropriate mindset would the willingness to work on the relationship. How to be committed, take responsibility means you will go the extra mile to see your relationship stays in the healthy zone, improve on listening skills, learn conflict resolutions, etc. When your outlook is positive, and are ready to take on the challenge of a new relationship (you will face a few), then you are marriage ready.
In case you wish to explore this more, please seek pre-marital counselling.
Counsellor at Happy Marriages