Dream only last's a few seconds after becoming lucid

I'm naturally lucid however when i was younger I would immediately wake myself as they were all in nightmare/scary scenario's ; However, now I'm unable to hold a dream for any longer than about 3 second's even though I can get lucid once every 3 or so nights (I had one 2 nights ago) and I'm not sure what I can do to prolong my dreams by any amont (even 10-15 seconds would be a step in the right direction for me)