Nightfall is a natural phenomena. The human body keeps on building up sperm and the body needs to dispense it. It normally occurs through masturbation or regular sex. The frequency of night fall or nocturnal emission varies from person to person. It's not really a problem and you don't need to worry. Doing kegel exercises can certainly help you get better erections. Different people can get erections at different times and if you are getting them every time except mornings then there is no need to worry...consult sexologist they will help you further Regards