i've heard about guys having issues like this. not me personally, of course. it tends to become more of an issue as our equipment gets older. apparently it can be quite an issue when it happens in the 'heat of the moment' so to speak. i've heard that the following is a good solution:
https://www.viagra.com/taking/tips-for-taking-viagra
don't let a soft 'brake pedal' get you down, my friend!