Some people believe that they must befall excited to accomplish an erection. Things don’t work exactly this way. It is perfectly possible to grow the excitement up to the point of ejaculating long before having an erection. And it is also possible to have an erection without being excited, as when we have a morning boner, for example.
A very common “mistake” (there are no mistakes in masturbating, only experiences) is to hurry with the excitement in order to obtain a quick erection. Such habit produces more premature ejaculations than deep-rooted erections. It is not our state of excitement that produces, maintains and increases the erection but our state of mind. What usually happens is that the excitement pleases us and thus changes our state of mind. But the real foundation of the erection remains in reaching that magical state of mind.