You may retire at any age. You can not start taking a workplace pension until 55 though, so you need to fund yourself. There may also be knock on effects to the State pension for not having paid in enough years.
Believe me finding things to do is not a problem. Finding the enthusiasm to be self motivating is more of an issue, at least in the early days when every day seems like a holiday and everything can be put off until the morrow. I hope most come out of that stage and start disciplining themselves after a while. I think it can be the big difference between forming an attitude of one's life no longer being important, you have no important role in life any more (having kids might help avoid that) and instead thinking you are enjoying the freedom to do what you want so much you should have done it years ago. But as mentioned, it is the finance that is the big issue.