Keep building and stop focusing on sites like that because it will drive you nuts.
Focus on making your site useful, getting relevant backlinks and your ranking will return over time.
That's normal for a fairly new site to experience fluctuations. Alexa just recently had an overhaul and what generally happened was newer and untrafficked sites got hit (dropped) while older, more popular sites got a better ranking.
Remember Alexa is just a stat. It doesn't determine how much potential your site has. If you focus on making your site the best then people will like it, link to it and your Alexa rank will improve.
Why did my Alexa rank disappear?
Linear Mode
