〜がち: (suffix) tending to; apt to; prone to (病気がち 'often ill')

Says that something often happens, usually something unwelcome.

Verb masu-stem or noun + がち. Examples: 忘れがち, 遅れがち, 病気がち. Usually negative, and describes a tendency in people or situations. Compare 〜やすい, which is just "easy to".