The first problem was deciding what to eat for dinner. After a large bowl of fresh fruit salad over late afternoon coffee with a friend, my inclination was to eat something light what with my master’s swim practice starting at 8:30 p.m. What sounded good?

Cereal.

And so I had two bowls of cereal for dinner followed by a yogurt.

That was mistake No. 1. Foods one can tolerate before a workout are highly individual. For me, this was not a wise choice. By the third 250, which including sprinting the middle 50, my gastrointestinal system was not too pleased with me. My pace slowed to complete the workout, though I get the “fast 50s” at a hard pace, slowing down the moderate portions to, well, slow.

But I survived the workout.

Then I got out of the pool.

And Swim Master Greg just shook his head at me.

Swim Master Greg shot some video of my workout and showed it to me. Even after concentrating on form, even after really thinking about finishing my stroke … I wasn’t. It was clear, even on the tiny iPod nano screen — my arms were coming out of the water far too early. I still wasn’t finishing my stroke. I still was failing to capitalize on nearly 40 percent of my power.

Frankly, I was bummed.

Since Swim Master Greg pointed out the lack of power in my stroke, my workouts in the pool have been centered and focused on completing the entire motion, on using that extra push, on feeling the glide. My presence in the water felt different. My arms were sore and tired in different (and good) ways. I thought I was making progress.

Alas, not much had changed.

My first inclination? To repeat the totally useless phrase of “I suck” over and over again in my head. To decide that I’ll never get this right, so what’s the use? I suck at this. Trying to correct this is an exercise in futility.

Oh, yeah, helpful thoughts (she wrote sarcastically).

But the important thing I’ve learned is that thoughts are well, just thoughts. Why can’t I have another thought? Thoughts are pretty easy to change. The pattern of our thoughts may take some time to alter on a permanent basis, but the initial thought? Well, why don’t I choose another one?

So instead of thinking that I suck, I thought how grateful I was to have a swim coach who paid attention to my stroke, who cares enough to help me correct it, who is patient enough to explain the same thing, over and over again, until I start to understand. I was grateful for the technology of the video camera, which was able to show me exactly what I was doing wrong  — and, let me not forget, the things I had started doing better.

No longer tumbling into the free fall abyss of negativity which parts of my mind seem to enjoy so much, it became easy to find things to celebrate.

My thoughts have turned toward eager — ready to get back in the pool and try some new approaches to getting the most out of my power.