Are people aware they are going through a mid-life crisis when it’s happening?

I think it's more complicated than that. Sometimes, you look around at the life you've slowly grown into and realise that you don't like it. That you're dissatisfied at the bone-deep level and need to make some large changes to get back on track to where you want to be. This can be a good thing. This can mean improving your diet, going to the gym, getting a new hobby, moving to a new town, getting a new job, or other general "life renovation" projects. Sometimes, though, this desire for change is brought on by fear or other negative feelings. Maybe you're scared of aging. Maybe you're looking at your newborn baby and feeling scared of being a parent. Maybe you're looking at your job and being afraid of failure, of the house of cards falling down. Change motivated by fear generally makes you do stupid things. Embrace risk-taking and spend irresponsibly to try and recapture your youth (you can't). Start having an affair to reclaim the person you were before you were a parent (you can't). Quit your job and start driving for Uber to relieve all that stress, only to find the stress right around the corner when you can't pay your mortgage. People call this a "mid-life crisis", but it can happen at any time. And it's not about whether you "notice it happening" - it's more like, do you recognise that the decisions you're making are bad, impulsive decisions? So, think to yourself. How many of your bad, impulsive decisions did you know were bad and impulsive when you made them?