(A)ntecedents (B)ehaviour (C)onsequences
Jennifer has stayed in bed all day. It's not something she used to do. She used to get up early, have breakfast, shower, brush her teeth, get dressed, make her family breakfast, clean the house, run errands, do the shopping, etc., etc. But those behaviours have all stopped. The one behaviour that has increased lately is that of staying in bed.
She's recently divorced, and both her children are now away at university. She is now alone. Thus the antecedents that prompted much of her prior behaviour, and consequences that reinforced it, have been lost. The prior behaviour has been extinguished, and Jennifer feels depressed.
Now that Jennifer feels depressed, her feelings of depression, tiredness and fatigue have themselves become antecedents: Getting out of bed, getting into the shower, brushing her teeth are now harder to do. She finds that staying in bed successfully avoids the additional exertion and fatigue that result from getting out of bed.
But staying in bed makes it impossible for Jennifer to lead a meaningful and productive life.
And if Jennifer were to get out of bed and head to the local supermarket, for instance, it's likely she'll bump into someone and then have to talk about the divorce. So it's likely she'll opt for the behaviour of staying in bed.
Given a headache (A), we take a pain killer (B), to relieve the headache (C).
Given a stressful social event (A), we have a stiff drink (B) to ease the social anxiety (C).
Given a ringing telephone (A), we pick it up (B) to stop the ringing (C).
Given sadness and loss (A), we stay in bed (B) to avoid the effort and pain of the day(C).