Price of Steem is highly influenced by the price of Bitcoin, so as Bitcoin goes up and down, Steem will as well. This is not an exact science, but more of a general way to look at it. Payouts happen after a week for SBD and Steem will sit with you until powered down.

Some extra info, you can kind of see what is happening with your account on these pages
https://steemit.com/@pauljameson408/transfers
https://steemit.com/@pauljameson408/author-rewards - You can see your intro post here earnings broken down, the default is 50% goes to SBD, 50% is turned into Steem, and then a percentage of that Steem is given to the people who upvoted your post. I think the final value of your post will really be determined when you spend the Steem or SBD you earned for it, as that is when you exchange it out for cash, goods, or services. Hope this wasn't too much information at once, this site is f'n confusing as hell at first, but as you understand it, it really isn't too hard. But know in the end even though you seen the price drop, it could easily double when you "cash out", but it could easily half too.