Can a person ever be too flexible?

Too flexible?: It depends on what you mean by "flexible." it's good to be caring of others and generous with yourself, but you also need healthy self-interest -- so you can look out for your own needs & wants as well. Otherwise, you could end up feeling resentful of the other person you've been trying to be "flexible" with. Healthy relationships involve 2 people, both worthy of consideration and care.