Made this mistake too. When I started back in paid employment I set myself ground rules of working when I am work, no email/messaging outside of work, arrive on time, leave on time, no overtime paid or unpaid, not thinking about work when I am not there, no socialising with colleagues and keep personal chit-chat to a minimum.

I found that this made me a better employee - focused on completing work quickly during the working day.

Easier to set these ground rules when you start with a company, also easier to set when you are 40 than 20.