Oh great question!!  I would do **so** many things differently ... if I knew the consequences like I do now.  I have too many "if onlys".  So to answer your question 

I can only live today like I have no tomorrow.  

It sounds trite but I have asked myself this question too many times throughout my life.  Your list is amazing.  And I can check off most of them, which, I know is so surprising since we share the same brain :)

I'm not living in regret though as a constant.  I have my moments where I wish I did this or that a lot differently.  Then after a while of self deprecation, I pull up my boot straps and join the land of the living again.  For that time I will laugh more, feel more compassion for others (instead of feeling sorry for me, wa wa), I will do things that I enjoy etc etc.

Life is messy.  And all we can do is be aware and attentive to what we have right now.

The end :)

ps - I forgot to mention your beautiful macro shots.  Excellent.  I love this little blue forget me nots - I think that's what they are anyways.  Have a wonderful day my friend.