We all have close shaves, most do not get reported, some are closer than others. In VFR-type flying there are some measures you can take to reduce the risk of a mid-air collision. Know the high risk areas - especially when joining a circuit. There can be particularly high traffic density around airfields with intensive flying training, 'Areas of Operation' have been added to VFR charts in Ireland to assist in identifying such potential threats. EINC, Newcastle airfield - just south of Bray Co Wicklow, is a busy area for uncontrolled GA traffic operating VFR outside controlled airspace. It has an ATZ established - the only one to date in Ireland outside controlled airspace. Always look and listen out for other aircraft nearby wherever you are near an airfield. Use the Radio and whatever means you have available to visually highlight yourself to others, make regular turns to expose blind spots (this may also highlight your aircraft to others). If you have a choice, dark colours are best for airborne visual conspicuity. Always have your anti-col and strobe lights on - consider landing lights also when in the vicinity of an airfield. Always have your transponder switched ON with mode C (altitude) active - more and more aircraft are equipped with electronic detection devices. Consider Electronic Conspicuity for your aircraft - ADSB in/out is the emerging future-proof technology. Portable devices are now available.
A VERY close shave occurred in the UK in 2019 involving 2 x light aircraft operating from the same airfield flying disabled children on local air experience flights. The AAIU summary below is well worth reading.
There were 2 GA fatal mid air collisions in the UK in 2011, both occurred in the vicinity of airfields and both involved aircraft rejoining the circuit, links below.
Other good reading material in the links below including an excellent GAPAN article that, while dealing primarily with sense and avoid safety levels for remotely piloted aircraft, has huge relevance for GA fliers.
Finally, a link to an EASA website on How to avoid airspace infringement & reduce the risk of mid-air collision.