How can one lower the gaze from forbidden things in the presence of temptations and ensure the resolve not to return to sin, which is a condition for repentance, especially when traveling and being in mixed environments like universities, which are difficult to change?

The most important thing that helps lower the gaze, after supplicating and seeking assistance from Allah, is to strive against one's self and restrain it from looking. With this striving, the matter becomes normal. A person is not held accountable for a sudden glance as long as he averts his gaze and does not look a second time. As for 'resolve', it does not mean never returning to the sin absolutely, but rather it means that when a person repents, he should have a firm resolve not to return to that sin. If he returns to it moments later, his repentance is not invalidated.