This is your Chiron return. Chiron follows an elliptical path around the Sun so it is unpredictable to estimate its journey through the horoscope by sign. But around 49-51 years it will make its return, becoming conjunct with your natal Chiron. This is part of what is considered the mid-life crisis. When this happens you will experience a reopening of wounds from your first Chiron square - the time in your life where you felt personally wounded for the first time.
Your first Chiron square happens between ages 3-23. As mentioned before, it is unpredictable and you must look it up in your epheremis. To look it up find when transiting Chiron hits the exact degree but three signs later (the same quality: cardinal, mutable or fixed) and makes a square to its natal position.
Chiron is retrograde quite frequently, so there may be several passes. You may not be able to recall or pinpoint a particular day for the Chiron square to be significant, but whatever event or feeling was going on during the time frame can be identified to have significance.
For instance, my daughter had her first Chiron square when her brother entered preschool and he received much attention from new friends, their parents and the teachers. Her Chiron is in Virgo so she was feeling less than perfect, and the transit was in first house Sag where she was wounded by trying to show herself shining over him to get attention. This took place throughout the school year. One incident, or several may have triggered her into feeling personally wounded at the time, but I don't remember.
My cgeneration experienced the first Chiron square later on, as a young adult. Check the Sabian Symbol of the natal Chiron and the degree of the square for clues.