Multitasking is one of the worst ideas ever to be conceived … do one thing at a time; do it well; do it right; then, move on.
Perhaps the above is overly simplified, but the idea behind it is really simple. Trying to do more than one thing at a time is simply asking to be interrupted at any conceivable moment; and, what’s worse about the situation is the one that will be generally interrupting you is yourself.
If you really need to get something done, then focus on that particular item and get it done.
If you have a list of items that need to be accomplished, prioritize them first; then get them done … one at a time.
You’ll thank yourself for doing this, twice. First for not interrupting yourself, and second for doing the job well and getting it right.