Its so hard when you fall in to that trap and not knowing which way or how to crawl back out of it again! However, try and take your time, try and limit the amount of times you do it and eventually wade yourself out. If you do relapse - forgive yourself and try again, and dont get yourself worked up about it whilst your in the process of healing. You claimed you managed to resist the urges once, then you can do it again

As for your friend, try not to take the comment too personally. SI is scary for others who haven't experienced it themselves and people react differently to it. Its hard for them!

Be kind to yourself and i hope you have a nice safe, speedy recovery