Bad advice, especially if you're under the age of 35 or want to evolve as a person.
I would suggest the exact opposite: do many things, fail better, be open to new possibilities.
I would suggest the exact opposite: do many things, fail better, be open to new possibilities.
The options become less less as you get older, obviously. In fact I think the best description of the change in career outlook as you get older is a switch from breadth-first search of new experiences to depth-first search.