work on technique, ^^^what you're doing there isn't it. Realize where you are as far as your fitness goes, take a normal route you generally do and start setting goals. hammering doesn't do anything other than burn you out, especially if you're by yourself. Conditions also make a difference as well as your preparation. If you ride ride ride, remember to rest, I tend to be fastest after a full day of rest and preparing, and that is usually the day I use to judge where I am ability wise, but being slow and steady and finishing with a decent average is always good. Theres nothing wrong with being consistent. I tend to see improvements when riding with another solid rider, it pushes me to push harder. Sometimes riding alone can leave you unmotivated to really push you to your limit.

edit: you might just be slow for life....sucks