Unless you've been having lucid dreams since you were a kid, it's close to impossible to have them frequently without any practice at all. I've been lucid dreaming for two years and I need to put my all to it to have a few lucids a month, and even so I go through dry spells now and then... Of course it's different for everyone, but for most of us it's practice and intention that translates to lucids. Don't be discouraged!