Today, I had amorning plans since the morning, so I had to get up early. Today, I had morning plans so I had to get up early.

After the planat, I had to write an experimental report. After that, I had to write an experimental report.

Already mentioned plan in previous sentence, don't need to say it again.

I'm exhausted but I haven't finished the report so I couldn't go to bed just yet. I'm exhausted but I haven't finished the report so I couldn't go to bed just yet.

However,Yet if I have nothing to do, I would sleep a long time and feel sluggish. Yet if I have nothing to do, I would sleep a long time and feel sluggish.

I guess busyness makestaying busy keeps me satisfied. I guess staying busy keeps me satisfied.