Successfully managing ADHD depends on self-awareness - and using your medication to your advantage.  Not every ADHDer needs medication, but if you are taking some, make sure you're using them to your best advantage.
Medication for ADHD is like a pair of glasses to help you see.  Glasses bring things into focus, but they can't teach you to read.  Treating ADHD is much more successful when you use cognitive therapy along with medication.  Please speak to your ADHD specialist about this.  Medication won't improve your time management, executive functions, interpersonal relationships or self-awareness, and all these things are essential to live your life to its fullest, with or without ADHD.
Learn what these medications do, how they affect you and how long they last for you.  ADHDers have two neurotransmitters in short supply:  norepinephrine and dopamine.  Your medication can help maximize the use of these neurotransmitters to help keep you on track and making better decisions.  Some medication can kick in within 15-30 minutes while some might take an hour to do so; some meds last three to four hours while others might last up to 14 hours.  These numbers also might vary depending on your metabolism, or on what you've eaten.  You must understand how your medication affects you to be able to collaborate with your physician in designing a regimen that meets your needs.  Do you have a work meeting at 9 PM?  If you take your pills at 7 AM, you're not likely to be at your best during that meeting. 
ADHD affects every aspect of your life.  It's not just about test taking or focusing during work.  It's about your family, your friends, your checkbook and your health.  What if, instead of a work meeting at 9 PM, you're hoping to make a favorable impression on a first date?  Or perhaps you're meeting with your ex over dinner to try to understand where things went wrong.  You'd better be able to focus!
Perhaps you aren't even noticing the consequences of being un-medicated in the evening.  Does your temper flare more than usual in the evening (and are you blaming it on being tired instead)?  Are you forgetting medication for other medical issues because you're unable to concentrate?  Is your impulsivity resulting in poor decision and risk-taking behavior more common at night?  Ask yourself if your medication is still around when you need it.
Getting an A on a test is terrific; and we all want to shine at our midday business meeting.  But let's get our priorities straight.  Your significant other, your kids and your friends mean a great deal to you, and they deserve to be very high on your list of priorities.  To live your best life, it's not much help if your daytime colleagues think you're great while your loved ones only see you during chaotic and problematic evenings and weekends.  Many of my patients take their medications to optimize their performance 9-5 Monday through Friday; some even take medication breaks on the weekend.  They say, "I need these meds to be productive at school (or work) but not at home." 
Of course, from my point of view, (I treat people with infectious diseases) their argument doesn't hold water, especially if their infection may have resulted from "risky behavior."  Looking at the big picture (your life) - and in my small part of the world (infectious diseases) - you could argue that you need your medication most at night and on weekends.
Work with your ADHD team to learn how to customize your medication.  Be frank and keep an open mind, but don't settle for a one-size-fits-all approach.  Your ADHD is unique, and so is the way your meds work for you.

Jeffrey S. Rapp, M.D., is an infectious diseases specialist who practices at Cedars-Sinai Medical Center in Los Angeles, California.