I can't say whether it is right or wrong to contact those who have past on.
My concern would be whether it is good to pull souls back and its effects upon that soul, simply by our day to day thoughts even.
I am of the opinon that we should let souls go, with the faith and best wishes that they will be just fine.
Now the difficult part, ATTACHEMENT. I am afraid to say that, it is our bondage to that other soul and perhaps acounts between us and them from the past which can cause us to want to call them back or think about them often.
We may try to justify attachement and label it with words such as love. Unconditional love does not cause sorrow.
We may also have to accept that some souls experience untimely death due to the settling of accounts from their past, possibly even past lives. Not always an easy one to take on board either.
If you love someone, let them go/ set them free.
love Al*