Just go back to the exhalation and recite your word. When done, take a deep cleansing breath and slowly open your eyes. Be gentle with yourself. Don't stand up quickly. Find a quiet setting with ample time to complete your session.
Most people choose the early morning or evening to do their meditating.
Pick a time that suites your lifestyle, but be consistent. Build up the time slowly until you can do 20 minutes. You might want to try two 20 minute sessions eventually, one in the morning and the other at night. If you can only do five minutes, don't worry. We all have our comfort levels.