As humans, we're creatures of habit. We tend to fall into the same routines day in and day out, whether we realize it or not. We can let this ruin our performances, if we form bad habits, or we can use it to greatly improve our stage presence by building a routine of good habits.
Think about how many people fail at keeping up with their New Year's Resolutions (have you kept yours?). The predominant reason for that is most people make their resolutions too vague. They say something like "I'm going to practice guitar five times a week." That's bound for failure due to lack of specificity.
Someone much more likely to succeed would be the person who says "I'll practice guitar Mondays - Fridays from 8pm to 9pm. And If I have to miss one of those practices, Saturday will be my back-up day from 8pm to 9pm." THAT person is bound to make that his practice routine happen. He has a plan. He worked a routine into his day. He played into the fact that we're creatures of habit and used it in a positive way.
As far as rehearsing for your shows, you should be very specific about when you'll do it, and what you'll be doing. You'll be much more likely to succeed with a rehearsal schedule by doing it that way.
It may be difficult to stick to the schedules you set for yourself when you first add them into your daily or weekly routine. That's why if you're vague about adding a new routine to your life, you're much more likely to stop doing it. Force yourself to stick with your new routine for a month. The first few days will be easy, since you'll be excited about it. After that it'll get tougher, but once you get to the end of the month it'll be old hat.
I wouldn't recommend adding more that one new routine a month. Focus all of your will power on that one routine for the entire month. By the time it's routine for you a month later, you can add a new one and focus all of your will power on that. Just remember to be specific each time you add a new routine.
For example, on July 1 you might start doing a vocal exercise routine every morning, from Monday through Saturday for twenty minutes when you first wake up. Stay with this and focus your will power on that.
Once you've powered through that and made it routine, you can add a new one. On August 1, in addition to your morning vocal exercises, you might add a performance practice. Every Monday, Wednesday & Friday, from 6pm to 7:30 pm. During those practices, you'll roll through your set list, practicing each song in a varied form of the original version, as mentioned in Part 1.
Keep building on new routines until you've added all the pieces you need to practice to be a great performer.