I think too much of something is never a good thing. Angels, like demons, can see the bigger picture, so my guess is they looked at your current spiritual progression and determined that you cannot handle too much of their energies. They can be even more intense than demons sometimes.
I work with both angels and demons, mainly because I believe balance is a necessary thing, though I occasionally do intensive work with one or the other depending on my current goals.
I find their energy to be fierce, and fiery, like strong sunlight. I have also met an angel whose power was so overwhelming, I felt like I was going to suffocate (not all angels temper their presence, I found out later, after almost wetting myself in abject terror).
Demons, for me at least, tend to be less overwhelming, and more earthy. I find them to feel more human like, and angels to be more cosmic and almost alien (though they can and do act very human, their energy feels very universal and extradimensional to me).