Literal translation
hold on to the branches
Meaning
take care, look after yourself
Explanation
This is the advice given to someone climbing a tree, so they don't fall. Climbing a tree is an image regularly used in Provençal to mean "taking a risk", hence the figurative sense: if you're taking risks, be careful, find yourself some support. The direct, concrete image helped it pass into regional French. When someone clings to you to regain their balance and catches you off guard, people also say, in playful antiphrasis: "hoou! Hold onto the branches!", meaning exactly the opposite.