Why spare time is a really bad idea
It is so much easier to protect key blocks of our time when we have a "because..." so, why not deliberately make sure there is one?
Why should we do this? Because:
Unallocated time is the most easily stolen
There are two reasons for this. Firstly, if people see that our time is not allocated to anything else, they will assume that it is probably available for them to use. Secondly, and most importantly, if we think of big blocks of our time as "spare" then we have little or no reason to try and protect them. This means we are far more likely to say "yes" when other people ask for that time.
Here is a little video fable about this very issue:
So the key to getting the most from your time is to allocate it to the the things that really matter to you BEFOREother people start asking for it. This is especially important when it comes to the end of the working day because so many companies have an unspoken culture that "Team players are willing to stay late at the office."
Most people are willing to do this on an occasional basis but to ask people to do it consistently is both abusive and stupid. Sadly, it is a very common practice, even though it does not really generate any extra results, and it can be very difficult to go against the flow on this.
One way to make it much easier to resist the pressure to give time to your work, that should really be allocated to your friends and family, is to deliberately put social appointments into your diary just at the point you want your working day to finish.
So, for instance you could go ahead and book that Salsa class at 6pm or drinks at 7. Then, when it is time to leave the office and you are challenged or you feel the eyes of doom burning into your back, you can say something like: "Sorry. Got to go. My Salsa partner is waiting for me." It is way easier than just saying "No. I don't want to."
Another helpful strategy is to block off some chunks of time during the day, just for yourself. They don't have to be long (10-15 minutes is plenty) but they put some breathing space into your busy day.
You can use them for thinking, or letting your overworked brain cool down. If you are on a shared diary, you could call them something like MMI Meeting so it looks official. MMI stands for "Me, Myself and I" or in other words "time to reflect."
You can find your own versions of these strategies but the key is to pre-allocate your time to the things that really matter to you.