If this uncertainty will exist at cube than I can't predict anything.
You can predict something: if you know the wavefunctions of the atoms in the box, you know the probability of finding them in (x,y,z,t) if you perturb them very slightly, with a soft photon, for example. In general quantum mechanical solutions do give predictions, their predictions have been checked against data of elementary particles many many times by now, and they are correct.
I always found the cat in the box an unfortunate analogue. That is because we also have innumerable measurements of macroscopic classical physics, with known equations and laws that are very predictive and work very well. A cat is a macroscopic object and there exists a transition region between microscopic and macroscopic physics which is bridged, among other methods by the density matrix view of the state. It is called Quantum Decoherence.
In quantum mechanics, quantum decoherence is the loss of coherence or ordering of the phase angles between the components of a system in a quantum superposition. One consequence of this dephasing is classical or probabilistically additive behavior. Quantum decoherence gives the appearance of wave function collapse (the reduction of the physical possibilities into a single possibility as seen by an observer) and justifies the framework and intuition of classical physics as an acceptable approximation: decoherence is the mechanism by which the classical limit emerges out of a quantum starting point and it determines the location of the quantum-classical boundary. Decoherence occurs when a system interacts with its environment in a thermodynamically irreversible way. This prevents different elements in the quantum superposition of the system+environment's wavefunction from interfering with each other. Decoherence has been a subject of active research since the 1980s.
In simpler words, when an enormous number of quantum mechanical entities (atoms,molecules, photons) are involved the problem becomes statistical and falls back in the realm of classical physics, which is strictly predictive.
If by "fate" you mean destiny, then the quantum mechanical level is irrelevant, because people move and live in a classical meta level and quantum mechanics rarely interferes with their life.
As @ChrisGerig says in the comment there is no experimental evidence that parallel worlds exist, so you can relax. It is just an extrapolation from the mathematical methods used to describe quantum phenomena. Would you worry if sine and cosine functions exist somewhere immaterial?
