Practicing can either make you excited for your progress or leave you wanting to take up something more interesting...like knitting. Sometimes all you need is to shake things up and bit and change your routine.
What to do when you need a change of pace:
Find a friend and play duets
Try a new warm up or play the scale game
Improvise (scales or make up your own piece)
Sight read new pieces (look on imslp.org or musicnotes.com for free music)
Learn a new extended technique
One thing that will help you enjoy practicing more is if it is effective. No one wants to waste their time in the practice room. Here are a few tips on effective practice.
You don't need to play through the entire piece every day. Chunking and practice boxes are two ways to get in good practice without tiring yourself out.
Try chunking (no it's not a new dance move). Take very small sections of your piece and play though it with different rhythms.
long short short
short short long
short long short
long short long
etc. etc.
Make sure you then connect the section you practiced to the next measure.
Another technique similar to chunking is to only work on practice boxes. Practice boxes are a few measures of the hardest parts of your piece. Pick a few practice boxes or lines and really focus on all aspects of your playing. Is your tone consistent? Are your rhythms correct? Are you playing with musicality even with scales?
Correct notes are better than a fast tempo. Studies show that the more a musician plays through a piece or passage correctly the faster they will improve even when less time is spent practicing. Don't rush through a with poor tone, technique, or articulation. Always strive to make each note beautiful.