Hrm .. been diving for 15 years now and the best advice I can offer is to remind yourself to just stop and experience - ie. live in the moment. You miss a lot of what is going on around you until you become more comfortable with diving, so look around, take it all in - you won't regret it (most times
). Aside from that, slow and controlled breathing will save you tons of air (thus provide more "bottom time").
Have fun!