One of my teachers had each one of us bring a clear plastic bag and a sack of potatoes. 
For every person we'd refuse to forgive in our life experience, we were told to choose a potato, 
write on it the name and date, and put it in the plastic bag. Some of our bags, as you can
imagine, were quite heavy. 

We were then told to carry this bag with us everywhere for one week, putting it beside our bed 
at night, on the car seat when driving, next to our desk at work. The hassle of lugging this around 
with us made it clear what a weight we were carrying spiritually, and how we had to pay attention 
to it all the time to not forget, and keep leaving it in embarrassing places. 

Naturally, the condition of the potatoes deteriorated to a nasty slime. This was a great metaphor 
for the price we pay for keeping our pain and heavy negativity! Too often we think of forgiveness 
as a gift to the other person, and it clearly is for ourselves!! So the next time you decide you can't 
forgive someone, ask yourself ... isn't your bag heavy enough?