From a feelings standpoint my mood changes and I can either:

• Feel flat
• Feel overwhelmed
• Be a bit sharp

My actions and behaviours are also a good source of signals that I need to tune into my feelings:

• Binge/mindless eating
• Withdrawal from people
• Inability to stop or relax
• Irrational decisions or thoughts
• Obsession e.g. a game or inability to let go of a task like doing personal finance maths
• I go in to autopilot

It might take time to recognise, but answering the question above when you’re in a good mental state can help you pick up on the signals sooner and take action to stabilise.