Terror vs. aerobic exercise: one week on the new bike

Terror and aerobic exercise are often difficult to distinguish.  Many of the bodily reactions are identical: sweating.  Heavy breathing--needing more oxygen.  Trembling.  Stiff muscles.

Last week I thought about this as I biked to school with Maybelle on the big girl bike, since I was having such similar reactions.  Was I terrified, or was I just exhausted?  Over the week I considered some crucial differences:

• The new attachment to the bike is heavy, and Maybelle's weight is in a new place.  This is having effects that aren't related to terror:  for instance, it's difficult to start pedaling from a stoplight (and please rest assured that I stop at every red light and wait for it to turn green). 
• Because riding fast helps this bike (and any bike) to be more stable, I'm definitely riding faster.  I know this for sure because I'm zipping through lights that, in the past, I always had to stop at because of the timing:  by the time I made it through one green light, the next one in line was red. No longer the case, and I know that they haven't changed the timing of these lights.  Ergo, I am faster.  Which is making me tired.
• I'm someone who's experienced a fair amount of anxiety in my life, and it's never made my thighs sore.  As I ride the bike with Maybelle, I can feel it--really feel it--in my thighs.

So I do believe that, after one full week of riding the bike, I'm experiencing a new level of aerobic exercise in my day rather than experiencing terror.  A transition has happened.  Maybelle and I are both comfortable on the bike.  She's going to continue learning how to respond to the changes in direction and angles that are part of being a bike rider.  

And I'm going to have bigger muscles.