If your email marketing is non-existent until you want to sell something, your subscribers know – even if you disguise it as education.
Burying your offer at first and then gradually ramping up the "aggression" of your sales pitch is also self-centered and obvious.
There's nothing wrong with selling, but if you're not willing to establish and nurture a relationship first then it just comes off as negative: desperate, unwelcome, deceptive.
Give me a sneak peek...ask for my feedback...put my fingerprints all over the thing and I am MUCH more receptive to the eventual sales pitch.
Well, you can, but from a customer/prospect perspective it definitely leaves a bad taste in the mouth – and you're probably leaving money on the table as a result.
/end rant