Unwanted drainage

Although nearing my late 20s, I still find I wake up with a 'wet' dream occasionally. Whilst a short moment of untainted bliss, this can still take it out of one somewhat. Particularly inconveniently this can sometimes occur when a big day at work is looming the following day (when daytime sprightliness is an important consideration). Unlike normal sex, choosing to avoid the activity is not an option as one cannot predict when the next one will be coming (so to speak).

a) Is this healthy/normal for a man of my age?

b) What can be done to prevent this (that doesn't involve the sexual equivalent of cloud seeding. nor rubber bands)?

Thanks all