knowing when too much energy healing takes place
Yes, it's possible to do too much energy healing ... you'll probably get an intuitiive sense about it if this happens.
For me, if I've done too much energy work, I start to feel a bit hyperactive or feeling too much excitent. Light bulbs start to blow, I get little electric shocks in my body .. Sounds good but it's actually depleting, so then I know it's time to slow down.
A good way of letting the body settle it's energy is to do a little barefoot walking, that connects you with the Earths magnetic force and you can release excessive energy that way. Some of Donna Eden's exercises in your garden or park will help with that. Also, washing your hands and feet in cold water helps to discharge too much energy.
Bear this in mind - there are two types of situations. Some people have under energy and some have over energy tendencies. I am the latter, sounds like you are the former. Both are out of balance - somewhere in the middle is good.
So just trust your intuition to tell you when you are doing to much, then back off a little. You can get along very well with the Donna Eden exercises and then have a private session every 2 weeks or so.