@oristarA,
Ori: it is not proper to say.
Summer and darkness can never stop you from longing for sunshine.
Because summer itself is usually hot or very hot; one needs not long for sunshine (rather, one longs for cool).
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What does "proper" mean, Ori? Your personal opinion doesn't prevent others from having a differing opinion. It's conceivable that there are people who would want 24 hours of sunshine and hot.
Ori: Likewise, rapids themselves are fast flowing water. That is why it is not proper to say:
Rapids can never stop a river flowing into the sea. Because rapids usually help water to flow more rapidly.
Saying "Rapids can never stop a river flowing into the sea" is like saying "sunshine can never stop water from becoming hot." It is improper because sunshine always makes water become hot.
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A number of fundamental errors. Methinks that you've never been in a set of rapids. Rapids often have boulders, some smaller some humongous. The slope creates the speed. The name rapids includes a greater incline/gradient to be sure but it also can have rocks, snags, boulders, eddies, backwaters, sump/souse holes, keepers, haystacks, hydraulics, ... , some or all of which slow and even reverse the flow of water.
See,
http://www.pinnacle-travel.org/whitewater-rafting-glossary/