I've found that stabilising to much does quite often end a Lucid prematurely because you're inevitably thinking of waking up.
Instead of trying to stabilise, learn a linking technique such as Spinning!
It's very easy and works pretty much all the time, then you don't even have to think about stabilising once the dream becomes Vivid, because you know if/when it fades you can just link into another one or back into the same one.*