You’re going to have dark days.
You’re probably going to have a few dark weeks.
And you may even have the odd dark month.
Whichever state you find yourself in, there will always be a positive or two upon which to focus. There’s always something that is going right or making you feel good, no matter how bleak the outlook is otherwise.
The trick – and this is one that gets easier as you progress through your PhD – is to be mindful enough that you can spot those few glimmers of positivity and focus on them more than you focus on the negative.
The more you can hone that skill, the easier it will be to deal with the dark times.