Even the best lock only buys you 2 minutes from a skilled thief. The location where you park and your ability to keep an eye on your bike are critically important. If you develop a habit of parking your bike at the same place and time thieves can take advantage of that and plan a targeted theft. If you can also demobilize your bike by removing a wheel, battery or seat it helps make the bike less desirable.
If you want get really depressed watch the lock picking lawyer on you tube. Most locks picked in under 30 seconds.