Two things come to mind ... the first is to keep a little spiral notebook in your pocket and write your passwords, duties, etc. down for each job so you have a good reference system. This has been very helpful to me in past jobs.

The next thought is that if you feel keeping two jobs going just isn't working out, you can quit one of them. It would be better to be successful at one job than mediocre at two.

All you can do is try, but give yourself permission to leave a job if necessary ...