I did a crazy thing this week. I signed up to run a half-marathon in four months' time. Me, a complete novice. Someone who hates running. Why? Because, crazy as I am, I love a challenge. They say running is all about mental discipline. It's just as well, because it's not the only race I'll be running in the next few months. I'm also entering the final straight of my PhD.

At this stage, the end is in sight. But getting there is still going to be a slog. The view is rather daunting, but I know I have to keep a cool head and take one step at a time.

In truth it's an exciting period in my PhD, a time of consolidation. Things are supposed to come together as a cohesive whole, although it sometimes feels like a frenzied rush. Will the experiment deliver enough data by the time I have to submit? I don't know, but that's the unpredictability of research. It doesn't always fit to a neat timetable and I may have to adapt, depending on what happens. At the same time I'm faced with major career decisions.

I think you have to trust that it will be all right. Writing up is a test of many things, chiefly patience, wits and sanity. I'm in for the long haul. It's too late to turn back now, but I believe it will be worth it when I cross that finishing line.