Dreams, split nights and what a sleep log can honestly tell you

Plain answers about dreams, about sleep that does not arrive in one tidy block, and about what a self-reported log can honestly be used for. Written to be useful whether or not you ever install this app.

• Why you forget your dreams within minutes of waking

  Dream recall does not fade gently over the morning — it collapses, and most of the collapse happens before you are properly upright. Here is what is going on, and what it means for where a dream note has to live if it is going to catch anything.

• Sleep is not one block: naps, split nights and the midnight problem

  Most sleep trackers assume you fall asleep once and wake up once. Plenty of real sleep does not work like that — and the calendar itself makes a night that crosses midnight surprisingly awkward to write down. Here is how to record the shape you actually slept in.

• How to keep a dream journal past the second week

  Almost everyone who starts a dream journal stops. The reasons are predictable and mostly structural rather than personal — the entries are too expensive to write, the habit is conditional on success, and nothing ever gets read back. Here is how to set one up so it survives.

• What a sleep score actually measures — and what it cannot

  Every sleep app hands you a number out of 100. Very few will tell you what went into it. Here is one score taken apart completely — the inputs, the weights, the grade boundaries, the things that were removed and why — and an honest account of what a number built that way can and cannot mean.

• What a dream reading can and cannot do

  Dream dictionaries will tell you that falling means anxiety and water means change. Nobody can honestly tell you that. Here is what is left when you refuse to make anything up — and why what is left is more useful than it sounds.