Keeping fit while traveling doesn't have to be a chore, or let go completely with a ton of excuses no one else cares about but you. There are ways to keep at it for free, and incorporate it into your plans for the day.
Here's how I suggest you wipe away the guilt.
Walking the San Francisco or Brooklyn Bridges are great challenges, and even if heights are not your thing, you don't feel that exposed. There are tons of others doing the same thing for exercise or a commute back and forth to work.
The Brooklyn Bridge is 1.1 miles. The San Francisco Golden Gate Bridge is 1.7 miles. How long it takes depends upon your pace and purpose.
As an example, I did the walking bridge level in Sydney, Australia - it took about an hour - and felt comfortable for picture taking along the way. (No selfie picture to prove it here.) The pararomic view of the harbor and the Opera House were amazing at sunset and worth the effort. ( I did take many pictures.)
Now try a suspension bridge that moves and sways along with you, and I have to tell you my heart beats a bit faster looking down into a deep river gorge surrounded by the jungle. That's not my cup of tea. Usually, I keep putting one foot ahead and looking to the other side for reference. Rarely am I one to stop and take photos.