No atom loses electrons easily, because the resulting positive ion attracts electrons.
An electron transferred from one atom to an other can happen in a strict ionic bond, when one atoms attracts the electron much more than the other does - AND it needs some mechanism to help the resulting ions keep stable.
In a solid, positive ions are closely surrounded by many negative ones (and negative by many positive ones) so that the electric potential of the ions is not too big.
In a polar solvent, liquid molecules put the end of opposite charge near each ion, which again reduces the electric potential.
Other bonds - which can be strong as well - rather put electrons of both atoms on a new common orbital, which can be more favourable than the separate atoms. And since most atoms are already bound in molecules (H2, O2, N2...) a reaction has to break the old molecules first, so it's a mere re-arrangement of the bonds.