

A little mental trickery you can use is to move to calculating how many hours have passed when you start thinking how many are left.
The brain is lazy, and creating extra effort will gradually make it avoid the original thought in the first place. It will also make you think about what you have managed to do, and the relax you have taken, instead of projecting into the things that are to come, that, since they are not already done, seem more tiresome.
This advice comes with 0 guarantee of success from a completely unreliable source. Take it with a grain of salt. In my case it works pretty well.
1996