How will it be?
Well a lot depends upon you. There are people who can't let go and there are people who can.
In my case flying was an intensive time lasting through RAF (to 30) Major airline (to 55) Startup airline far away (to 57) LOCO in UK and then "abroad" (to 60) and then...
Retirement!
Many things then change - number one, you are at home all the time and interfere with the daily routine of the person(s) who has spent years coping without you. This takes patience and adaptability on both sides to deal with.
You wake up at 04:00 and realise that you don't (ever) have to get up and shave and scrape off the ice and drive to work. It's a nice feeling.
You hear / see jets and (this is where it varies according personal makeup) either you think "I know what it is like and I don't need it now" (my case although I loved it at the time) or you feel "I wish I could still be at the controls" (some friends of mine).
You don't forget all the skills and experiences which were, during your career so vitally important - and made you important too - which now count for nothing - and you might regret that initially. Try to keep the knowledge that "you can do it" in the bank as a confidence booster.
You have a need for something intensive to take the place of your intensive job. Actually this is not such a problem! You can dust off your old bike / skis / lathe / walking boots / sports car / spade / dinghy and get in some quality time. You will slow down in good time - meantime enjoy the activity.
Your life is not ordered by a schedule. So it is actually quite important, after the initial luxurious lazy period, to make your own schedule. Try to get one useful thing achieved each day, even if it's ringing Mum or ordering your paperwork. Pretty soon a meaningful routine will be achieved.
Have something to look forward to. If you like travelling - plan a trip. If you like your home, plan some work on it and the garden.
And here, let us say that PPRuNe is a good way to keep in touch with the old life and mates (though the internet shouldn't be allowed to soak up all your valuable time!)
Lastly, enjoy this last year - remember the good things, laugh at the bad ones - there is only a year of them to put up with.
Good Luck,
FC.