To Brood
To Dwell On, To Take Something To Heart
transitive verb, ichidan verb
詰める is "to stuff in." If you're really stuffing in your thoughts (think), you're thinking very deeply and seriously. So this is to brood, to dwell on, or to take something to heart.
思い詰める suggests you're pondering deeply over something serious or distressing, bordering on overthinking.
The reading is 思い and 詰める put together into one reading.
失敗を思い詰めることで、ますます不安になってしまったんです。
By obsessing over the failure, I became even more anxious.
思い詰めていた気持ちを誰かに話すことで、少し楽になったりすることもあるんだよ。
Sometimes, talking to someone about the feelings you've been preoccupied with can make you feel a little better.
私は失業中ですが、そのことを思い詰めてはいません。
I'm between jobs, but I'm not worrying too much about it.
彼女のことを思い詰めていたけど、気づいたんだ。愛は自分自身を大切にすることから始まるんだって。
I was so absorbed in thinking about her, but then I realized. Love starts with taking care of yourself.