Not preparing for marriage ( or anything else), is just like blind folding your self and crossing a deep pit With the expectations of not getting injured or hurt (almost impossible).
Before preparing there must be expectations ( what must be achieved must be known). Expectations is actually the foundation for preparation. Once you know what you want or desire, it helps as guide or a form of direction in other not to be lost or get caught up in feelings which would not be productive.
One very important thing to note is that, your expectations should always be flexible ( not too flexible) because no one is perfect, and everyone in this world is growing on a regular basis. Always trust each others process, and be sure that at the end of the day, that The product of your process will definitely end up being your expectations.