Many musicians enjoy playing and that's it. They take their instrument and play again and again what they already know well enough. This will take them nowhere. They'll get bored fast and will play less every day. Yes, it's important to enjoy playing and it's fun to play again what you already acquired but this is not enough.
Spend at least 50% of the time you hold the instrument in your hands studying new things. Do you need some ideas? Have you done all the licks at Guitar Solo? Jamming with Band in a Box is a great way to go to achieve a better level and to have fun at the same time. When you listen to radio or look to the TV, take your instrument and try to play along with music you hear for the first time. Play with your friends, you always can learn from them, doesn't matter how good they are.
Learning music must be fun. When you feel you're bored, go to the next exercise then go back to the boring part and remember: what you don't finish today, you'll have to finish tomorrow.