If this is a initial stage of your seo process then don't worry fluctuation happens just be regular with your seo activities.
I lost around 700-800 traffic a day since last week (now at around 2,800 a day), not sure why, sigh. It's so hard to break through the 3,500-4,000 a day barrier
I think you lost your website poor quality links that's why your keyword rankings will drastically down.. the standard quality backlinks will never gone from our website..So for getting the quality backlinks do some off-page seo activities they will automatically bring the quality backlinks to your website, this leads to increase your website PR..i.e.: - Through Forum Commenting - Through Blog Commenting - Video Marketing from Video Sites like YouTube, Vimeo, Daily Motion, Flickr, Meta Cafe... or Other Business Sites... - Link Wheel Through Web 2.0 sites.. - Ads Posting through Classifieds - High PR Directory Submissions - Social Media Effects
IF Your site ranking is going down. Then Change your submission Content and create a unique article and do work in high page rank sites and do follow sites. Check your old submission Sites and where your website is not shown and do a again submission with unique and effective. Then you will get result or traffic.
May be your site affected by google recent algorithm update. I suggest you to change your site content and do some needed changes.