In reviewing this How to Install Undermount Sink video, I found it actually took 45 minutes of work to finish the job! Now that may seem like a long time, but in reality, a job well done means not going back to fix a problem.
And remember, "Patience, Patience, Patience!"
A "fussy job" such as this is a morning task I need to do when I am fresh. As a rule of thumb, plumbing is something I prefer to tackle in the a.m. There are so many variables that can come up when working that a fresh outlook helps the situation. I have learned (although not always) if frustrated with a project, walk away from it for a bit. Take a break and let your mind wonder from the subject. Going back to the task in fifteen or twenty minutes will almost always allow you get back on track. I know it helps me!