I started flying 40 years ago, yes, much of my flying has been in protected airspace, but I also am still current flying light aircraft and have kept it that way right through and have many hours flying GA, many of those years before the days of Collision avoidance systems, in all that time I have rarely (unintentionally) come close to another aircraft and rarely even had to change direction to avoid, that is not to say don't keep a good lookout, but it IS a big sky and you should not get excessively worried about this. DO take sensible measures, keep a good look out, avoid high congestion areas where possible and fly heights that others regularly fly (e.g. 2,000/2,500/3,000), but don't obsess over it!
