For me getting bored with practicing comes from doing it for the wrong reason. I practice to maintain and improve, to get a new piece under my fingers. So all the time I'm concentrating on what I'm playing and how I can make it better, or even just get it right. This puts the mental focus on the result, not the tedium of the repetition. And when I'm getting stuck, I either put the fristration to good use by telling myself I'm not going to let something beat me. Or I take a break, play something just for fun, then get back to it.
Necessary evils like scales can be made more interesting by varying them - for instance instead of simply playing 1234567876554321 play 123 234 345 456 567 678 876 765 654 543 432 321, then repeat over two octaves. Then try playing it in 3/4 time, emphasising the first note of each group of three. Try swinging the normal scales. Then swing them backwards. Go from scales to arpeggios, try different patterns to the one I showed (like groups of for or five).
Also in exercises play each note as beaautifully as you can. Or as dirtily... Practice growling through a scale. Play low Bb like a foghorn, then subtone it. If you come across a tricky note sequence in one of your pieces, work on it alone. Get the fingers moving as you need them, then go back to the piece.
Even long tones can be fun if you use it to improve sound, note stability, volume control (without pitch changes)...