Harder Erections

I was just curious if anyone could answer this for me……..Why is it sometimes I get really rock hard….and then sometimes I don’t…..it is really inconsistent…..granted I’m really lazy….would it help it i did the exercises listed here and also just normal daily exercises also? Any info would be great…

I have no idea. Mine are always rock friggin’ hard. Taking pictures of my penis with a ruler on the table is quite the challenge as it gets rock hard in the full upright position. :P