I think this is a really important concern. Btw, 5% is still quite a bit more than the average, so good work!
We're attempting to overcome this worry through community and behavioural economics hacks. E.g. I take every opportunity that I can (like this one) to say publicly that I'm planning to give away the majority of what I earn, which makes it a helluva lot harder for me to back out. Similarly for Matt - it would be embarrassing for him to renege on his commitments when he's been so open about it. And it feels like a much smaller sacrifice (if it's even a sacrifice at all) when most of your friends are doing the same thing - and some, like Jeff and Julia in Boston (http://www.givinggladly.com/2013/06/whats-it-like-to-give-ha...) are doing much more.
We're attempting to overcome this worry through community and behavioural economics hacks. E.g. I take every opportunity that I can (like this one) to say publicly that I'm planning to give away the majority of what I earn, which makes it a helluva lot harder for me to back out. Similarly for Matt - it would be embarrassing for him to renege on his commitments when he's been so open about it. And it feels like a much smaller sacrifice (if it's even a sacrifice at all) when most of your friends are doing the same thing - and some, like Jeff and Julia in Boston (http://www.givinggladly.com/2013/06/whats-it-like-to-give-ha...) are doing much more.