Have a good practice space with minimal distractions
This can be limited by your living arrangements, employment and a number of other factors but wherever it is make it somewhere that’s comfortable and puts you in a good mindset. This might mean having some natural light through a window to make you feel alive or a quiet dark room in the basement away from the rest of the world. Phones, computers, knocks at the front door can all be major distractions too so keeping these at check (as best as possible) is obviously a priority too. Another obvious point is having your instrument readily available. Inspiration can strike at any time so having your bass/trumpet/zither etc. setup and ready to go means you can get into practicing as opposed to spending 10 minutes getting it out of the case, assembled and tuned up. Sometimes the very thought of that rigmarole is enough to put off practice in the first place.
Write a list of things you want to achieve/get better at. This can be as vague as ‘I wanna be able to shred’, ‘I want to get some Latin gigs’ or super specific ‘I don’t know what to play over dominant 7 chords’. Getting these ideas down is a great achievement in itself. Have a good think about them and keep adding to this list over the next day/week/month/year. If some topics have priority over others put them into an order, otherwise pick one topic as a starting point.
Break it down and be realistic
This is not meant in a negative way. It’s great to aim high, but unrealistic goals might do more harm when you don’t achieve them putting you off even further or getting you into a negative mindset. Almost anything can be broken down into smaller chunks, and often these chunks are easier to deal with. Memorising the changes to 30 standards is a great goal but learning them thoroughly for a gig in a week’s time is perhaps unrealistic. Make the goal five standards instead and have the other 25 as tunes that you’ve played through and have charts for the gig and will work on over the following weeks. Being realistic can also help you see progress which in turn spurs you on even more. Any sense of achievement, no matter how small, can be enough to keep you practicing rather than feeling that you’re going nowhere and getting completely discouraged.