There are several reasons fish are lost. Line is the weakest part of the tackle chain between the reel and hooked fish.
Weak line due to age or knicks is a problem. It’s best to change monofilament periodically. You can slowly and carefully run monofilament line though your lips to see if it has bad spots or knicks in it. The wear areas are typically within the first several feet from the end of the line.
Another solution becoming more popular is the use of braided line. Braids with better characteristics now available so fishing them isn’t as frustrating as a decade ago. The braids are very small diameter, strong, tough and do not stretch. 15-pound braid is the diameter of 3- or 4-pound monofilament. The line is also more sensitive to bites.
The number one line problem is a weak knot. A poorly tied or old knot will always be the first to break when pressure is applied. Learn to tie a couple different strong knots and retie often. -TH