1. When you aren't open about your basic expectations like when to "talk", and how much "intimacy" you are comfortable in just because it might upset or freak out your partner. You just start living in periods of stress and confusion. These things are vital and if discussed openly and properly can bring a sense of calm and understanding in the relationship. You should not be ashamed of telling your partner that you don't like being ghosted or you aren't comfortable in some other things related to the relationship.
2. When you expect a relationship to end in marriage just by knowing the person for a couple of weeks, you are automatically setting a high bar for the person ( we want the ideal person to marry, right? ) and the person cannot just fit into your expectations without even knowing your expectations. Because you know each other with a lot of time and space. These things are very very complex to know within a span of weeks or even months and years. How you resolve conflicts, how you communicate with each other, what is your love language, how both of you coordinate in house chores( if you live together) and endless factors should be taken into consideration when you are taking it for the long haul. But these things require sinking in. Day dreaming about marriage can come later on when you are mingled well with each other.
3. Not being honest in the beginning or just plainly hiding the things that you "know" Might be significant to your partner is a very immature thing to do because later on it is bound to get hurt for both of you. If the person isn't comfortable with some aspects of your life right now, it would be too much to expect him or her to be comfortable with it later on too. Just being more attached doesn't mean that your partner will have the power to forgive you/ accept you, especially when you have been dishonest for a long time.