One great way to stay motivated is to cheer people on in these message boards. I'll tell you how to do it.
1) Communicate that you heard them. Either identify with them ("I know how you feel"), or validate their feelings ("That sounds just awful"), and perhaps ask a clarifying question (Help me to understand . . ."), though don't expect an answer--this is how you can qualify any advice you give, that you didn't necessarily understand the whole issue.
2) Be upbeat. Some useful ideas, it's a new day tomorrow, there are some really great articles on that, use exclamation points and emoticons
You can choose a bunch of them by holding down the "m" key, and then cut and paste them over and over to create a pretty pattern at the bottom of the message (highlight the HTML code for the emoticons, then use ctrl-c to copy the highlighted block, position your cursor to the end and type ctrl-v a number of times, perhaps 8, to create an eyecatching pattern).
3) Do some legwork, do a search and provide a link to the some helpful reference material.
4) Even if you don't know what the person should do, tell them something that worked for you or someone else you know. It doesn't have to be about diet either--fashion guidance might be appropriate! These people may be at wit's end on what to do, and they need a breakout from their own perspective. Then maybe they will be able to come up with the right answer for themselves :)
4a) Often there are personal boundry issues that come up. Try to point them out gently, that they shouldn't be worrying about what Aunt Margaret thinks, and the ex-boyfriend, well, that's why he's an ex, and the scripts he put in their head should go away too. Whatever.
A minor don't--don't make your answer too much about you. A short example is enough, the reader will fill in the rest.
For every one person who posts, probably 10 will read the post, so, even if no one writes back, that's fine. They heard and so did a few others.
And the best part about all this, is when you lift someone else's spirits, your own will be lifted as well. I don't know what sort of strength this is, that helps us all go on together, but fitness and diet are not enough, we have to be healthy in heart too.