To the OP, some perspective from someone not yet retired (but could retire now if I chose to):
1. I've spent my whole life aiming for something, working at a career, is it really over?
I didn't aim for anything other than a job that I would enjoy and which paid the bills. I am still shocked at being paid so much for a job that many times felt more like a hobby. But I have always viewed my career as a privilege, so never invested in making it my full identity but just a part of me... when it is over I have other things in my identity that will fill the void.
2. I feel as if I add value at work, but....
There becomes a trade off where adding additional value, even with rewards, is not worth it as it takes too much out of me. After a point the 80-90 hour weeks took more out of me and I chose to give that up even if it were perceived that I added less "value".
3. I feel frustrated that we can all see the inefficiency in the organization, and...
One of the benefits of experience is being able to put that frustration in proper perspective. Perhaps because I've been with Megacorp 36+ years. It is easy to remember the frustration, but in truth there have been more than enough episodes of joyful productivity to make up for up. At this stage in my career I'm moving into the "go with the flow" mode - not hindering my co-workers or those that depend on me, but also not letting the frustration get to me.
4. i have seen colleagues die and after a couple of days mourning, someone is in their office and the world has moved on.
I realize that is just part of life. Another reason ot to identify too much with ones career. Reminds me early in the career when I was working lead on a project and came down with a bad cold. After the 2nd day in the office in that state my manager sent me home and said "stay home until you fully recover. You are a great worker but we survived before you got here and we'll do fine while you are out." He said it with a smile and laugh, but I also saw the truth in that. That is another reason I have lessened identifying with my career.
5. Will I be bored in retirement?
I used to think that - and I am amazed at how many folks, when the subject of retirement comes up, also express that. I have taken enough "staycations" over the last several years that had me doing so many fun/challenging things outside of work that they went too fast, and I can see I won't be bored. Worse case... there are always others you can help with your time, and I have never found that to be boring.
6. I think I might want a really expensive car 
although I know they are a total waste of money
I've observed that many of my well-off friends who have retired actually go "low key", with comfortable but not expensive things. That is my nature... I guess I'd rather have folks think I was "struggling" when it comes to material things. What they don't know won't hurt them.
7. What happens if 12 months down the road I realize its a mistake, but..
Worse case, go back and do something else. Interestingly, where I live there is a steady and growing demand for temporary or part time workers. The advantage of being retired is hat you can be much more flexible if you are FI and decide to "un" RE.
8. I want the freedom to just be.....lazy
Nothing wrong with that. But sometimes lazy is the eye of the beholder. I remember having a fun day learning a new technology, and worked on it at my desk for the entire day. To one of our kids, it looked like dad was "doing nothing"... but I was quite engaged in learning, coming up with and testing ideas that I though would be useful in projects, an even walking around the house just having creative thoughts. One person's lazy is another persons' creativity.
I'd probably say that my only real security is not with me but for others. At this point, from a cold financial view, I'm more working now to be that "emergency safety net" for them. I am also able to more easily help family and friends financially if needed without impacting our financial situation. Some of this would stop if I retired. However, I am VERY fortunate in that DW puts my retirement plans over our income (In her words "I've rather have exciting years with you pinching pennies instead of being a rich widow"). While some of our kids have had their financial struggles, now that they are all adults they do not ask for handouts and now listen more to my financial and career advice. They (in their words) are now appreciating the foundation DW and I tried to put down for them. So maybe it is really more my "ego" at cutting back on being a good provider... but the family seems relaxed about it and I am learning to be, as well.
