Take the time to rehearse the parts to get past the "reading it" to the "feeling it" performance.
Believe it or not, many people, especially those at the higher levels of this art and business can tell in 3 seconds if the singer (and musicians) are faking it or feeling it.
I sent a song to someone pretty high up the food chain in Nashville, and the first comment the guy made after the song finished was, "she sounds like she was reading that lyric"... and while she has a good voice, the guy was dead on correct.
Nothing beats planning. Take the time to structure the song before you start recording it. Have a general idea what parts are where, how long they are, and what comes next. It's good to allow some creative space in a song because as I record, I very often see something in the song that would work better or something that needs to be changed because it doesn't work as well as I first thought.
Rehearse the parts as many times as is needed to get it natural and as close to perfect as you can... then hit record. I very often take a fair amount of time working out a guitar part (solo) and then after I hit record, I will find that multiple takes are needed to nail it and the part will often change drastically during that recording part of the project. A 15 second solo may take over 60 minutes or more to get right....and other times, the first take with record on, nails it. Hard to predict. But you will know it when you hear it. Point is, do it until it's right and it feels natural.
I always try to record the tracks with the end in mind. I know that at some point I will be mixing and polishing the project and I want the tracks to be as smooth going into that stage as possible. BUT... always focus on the job you are doing. If it's singing..... be the singer and not the engineer. If it's the production you're working on, produce the heck out of it. Of course, saying that is easier than doing it especially if you are like most of us here.... we do it all from tracking to final product. So the lines between musician and engineer tend to become a bit blurred at times.
The point is, try not to get too bogged down on any one thing. When I find myself losing focus on the project or starting to second guess the EQ settings on the bass track and such things..... it's time to recognize it for what it is and either move to something else, if you still have a good level of creativity and energy flowing or.... shut the DAW off and go do something else. The beauty of having the home studio is that rarely are we on a deadline or a time line of any sort. We're not paying for studio time by the hour and we don't have some record company breathing down our necks for the finished project. So feel free to walk away and come back tomorrow and see the project with a fresh perspective.
I find that even when I have a good level of creativity and energy flowing, the maximum I can work before I start to drift a bit is 2 to 3 hours..... sometimes more but normally that is it. I need a break. I will shut it off and walk away. At times, I can return in an hour, recharged and have another go at it.... and other times it might be several days before I go back.
I hope this helps.... anyway, that is my personal observations and practices.