Despite sleeping for 7-8 hours every night, I feel extremely sleepy each morning. How do I change this?

Sometimes, you may feel a bit dizzy when you wake up. A cup of coffee or a hot shower will most of the time solve the problem. But if you regularly wake up tired and feel tired all day long, there must be something wrong.
Sleep Inertia 
You may just be experiencing sleep inertia, a natural part of the waking process. The brain typically does not immediately wake up after sleeping; this occurs gradually. This transition period may cause you to feel dizzy or disoriented. In this case, you can easily fall asleep again.
Your brain and body are slow to respond after waking up due to sleep inertia, so it can feel impossible to accomplish anything when you first wake up.
Typically, sleep inertia lasts from a few minutes to an hour and usually disappears within 15 to 60 minutes. 
 
Sleep Drunkenness
If you awaken from a deep sleep feeling confused within a few hours after falling asleep, you may be experiencing sleep drunkenness. 
Sleep drunkenness, also known as confusional arousals, bypasses the inertia phase of sleep.
Commonly, it lasts between 30 and 40 minutes. You may not even remember it happened when you woke up the following day. You may suffer from sleep inertia or sleep drunkenness when you: 
• Get too little sleep 
• Awaken suddenly from a deep sleep 
• Wake up earlier than usual
In addition to shift work sleep disorder and obstructive sleep apnea, some forms of circadian rhythm sleep disorder may also contribute to sleep inertia.
Although sleep inertia is a normal part of waking up, you can minimize its effects by 
• Sleeping well
• Taking short naps 
• Starting your day with a cup of coffee 
Consult your physician if the symptoms persist. An underlying sleep disorder can be ruled out.