for me it helps to stop for some seconds.

when you get lucid do a long nosepinch but breath deeeeeply in and out again. Tell yourself this is YOUR dream nothing what was going on matters. think about what you want to do and when you remember your goals (in best case you incubated them during waking) you start doing them. Having goals helps you to stay focused and dont loose lucidity just like that. when you dont notice your lucidity slipping repeat the beginning tip every few minutes.
when you want more details hold on and take your time to SEE or HEAR or FEEL the details. focus on something and examine it (this stabilizes the dream too btw) the longer you look on a wall and touch it the more detailed it gets.

another thing is daypractice. when you practice mindfullness and beeing in the moment and looking for details and not just autopilot thru life your dreams will be equaly more detailed and you wont loose focus that fast. the way you are in waking the way your dreams are (plus the impaired mind)