I was looking for really good explanations of both. Wikipedia nailed it:
Self–preservation is a behavior that ensures the survival of an organism. It is almost universal among living organisms. Pain and fear are integral parts of this mechanism.
Self–expansion is based on two key principles. The first is that humans have a primary motivation to self expand. The second principle is that individuals often achieve self–expansion through close relationships which allow the inclusion of the other in the self.
In other words, self-preservation is when you live your life on survival mode. For example, you hate your job, but you work just to pay the bills. You often feel demotivated and exhausted when your day is over. Another example, you are unhappy in your relationship but you stay because you are scared to be alone. Self-preservation fuels on the fear of the unknown. We often self-preserve to avoid what we think would cause a lot of emotional or physical pain. However, since our soul is always calling us to expand and progress, self-preservation can only go so far because we often reach a point where our comfort zone starts feeling really uncomfortable. That’s what a lot of people would call the “wake up call.” Your soul knows there something better for you outside of your self-preservative walls and it’s calling you to get out. It could be traveling, trying a new career path, starting a business, writing a book, ending or starting a new relationship, getting closer to nature, adopting a new pet or getting closer to yourself.. etc. Whatever that call may be, never second guess it. Break the patterns that are no longer serving your growth. Our soul always knows best. And our soul knows self-expansion is the reason why we’re all here.
I wish infinite love, health, healing, wealth, success, happiness, awareness, peace and wisdom upon your soul