Psalm 129:2 means that the speaker (likely the nation of Israel collectively) has suffered oppression and hardship since its beginnings as a nation, but despite all these trials, the attempts to destroy them have ultimately failed.

Here's a breakdown:

"Many times they have afflicted me from my youth up..." This refers to repeated suffering and oppression that the nation of Israel has experienced throughout its history, starting from its early beginnings (e.g., slavery in Egypt). The word "afflicted" emphasizes the deliberate and harmful actions taken against them.
"...yet they have not prevailed against me." This is the key takeaway. Despite all the attacks and hardships, the nation has not been destroyed. They have survived. This demonstrates resilience and God's protective hand in their survival.

In essence, the verse highlights Israel's long history of suffering coupled with their miraculous perseverance. It's a statement of resilience, faith, and the enduring nature of God's promise to preserve his people.

The phrase speaks not only to the historical struggles of the nation of Israel but can also be applied more generally to the individual believer who faces trials and tribulations but finds strength and ultimate victory through faith and perseverance.