I retired almost 5 years ago, aged 59 - so similar to you.
I love it!
DH is also retired, and it means we get time to do a lot of things together - things that we never had time to do when we were both working, such as day or overnight trips away, walks in and around London, long leisurely lunches, trips to the cinema/theatre, etc. 'Long weekends' can now happen during the week, which takes a lot of pressure off - not having to get away early on a Friday or back late on a Sunday, for example, and as we also have friends who have retired, we get to spend more time with them.
Being the age we are, travel is free (in London: tubes, buses, trams, trains), and with a senior railcard, train fares around the UK are usually 30% cheaper, so it does make getting out and about easier.
Holidays no longer have to be 7 or 14 nights, but can be as long (or short) as we want. And we aren't restricted to an annual number of days we can take either - as well as being to make decisions about going away more spontaneously.
I can't tell you what a joy it is to not have my life ruled by the alarm clock or other people's demands on my time. I suffer from insomnia (something I always thought would stop when I gave up work, but sadly it wasn't to be!), but knowing that I don't have to be up at 6.30am, and that I can sleep for as long as I want to, when I do finally get to sleep, is so much more relaxing.
What I wish I had thought about more, when we were both earning, was taking account of the things that needed to be done around the house, and doing some things earlier - or at least to seriously consider how much money we were going to need for them (e.g. having to have the outside of the house painted, having to replace a lot of carpets,) and also allowing for the unexpected, e.g. having to have new roof tiles and guttering after leaks, the car needing major repairs. At some point various other things will need to happen, and although we have a healthy retirement income, some things take a much bigger chunk out of your money than you might expect or have planned for.
Losing your identity @BermudaBlues is an interesting one - it suggests that you define yourself by work. I'd be working on that, so that you have a definite sense of who you are, and your worth, before you give up work. I'm also wondering why you might thing the dynamic of your marriage might change?