Pick one thing…
Pick one thing to start every practice session with. Make that the first thing you do every time you sit down to practice. This way, you will have a ready doorway into the peaceful world of practicing.
Back when I was riding my bike a lot, sometimes it was a challenge just to get on the darn thing and ride! I made a habit of telling myself, "OK, I'll just put on my shoes..." then, I'd tell myself, "I'll just clip into the pedals..." Next thing I knew I was halfway to Multnomah Falls on a beautiful day (even if it was Portland-rainy) and feeling really good about it.
Here's the point: practice is something we WANT to do, remember? Sometimes our crankiness or laziness lets us forget that. So, to make it easier to get into the flow, instead of thinking about a big stack of stuff to practice, or about how long it will take, just tell yourself, "OK, I'll just sit my butt down and start with the thing I always start with and work my fingers for a few minutes..." Chances are, you will make that shift and regain your enthusiasm to tackle the rest of your routine, wondering why you ever thought you would do anything less.