Ann: Mukuyu-1 Sidetrack Wireline Results Indicate Multiple Zones, page-124

You can yank on a wireline which is what you usually do when you get stuck but there's a limit as to how much tension you can pull on the cable. The cable has a breaking point.....usually operators will not pull more than 75% (from memory) of maximum safe pull.
There is usually also a weak point located inside the tool head. These weak points are either mechanical (ie they part at a known tension value) or electronic (they release when a signal is issued from the wireline unit). Electronic weak point will also have a tension value at whch it will mechanically fail.

If you yank on the cable without paying attention to cable maximum safe pull and weak point specs you run the risk of parting the cable and leaving a tool with no cable attached in the hole or worse...a stuck tool with a birds nest of cable sitting above it. Both situations reduce the chances of a successful fishing job significantly.

We currently have a tool with cable stuck and still attached to the tool. The best scenario for a straight forward strip over fishing job.