In my opinion it is best to work on one song at a time. I have found through working on to many songs at 1 time you can easily get frustrated and annoyed. It is best to keep it simple.
1: Work on one song and get it right and sounding how you want it to sound, also don't be to up your self and use a metronome. It really helps in my opinion.
2: Get the basis of the melody down and then add extras. I have found trying to add to many instruments and percussion before you have thickened the melody can be really off putting. Get the melody right and it will all fall into place.
3: save the best until last. always add your solos at the end and do not go over the top keeping it simple yet a little complexed can really add to a song. also adding percussion can really help fill out a song that may be sounding quite flat.
these rules are what I live by and I have created some decent music just by keeping these steps in mind. If they work for me they could also work for you. :)