How long is it suppose to be..

Every time I write a blog I never know exactly how long it is suppose to be. How long is long, how short is long, how long is short or hor short is long. i know it makes no sence but it's a honest question. Should I write a whole paragraph all the time or could I just place a few sentences on the blog. Somethimes all I place on the blog is how I feel and sometimes it really only take a sentence to reveal my inner most feelings. Sometimes a word is good enough for me. I could honestly come to this blog and write, "....better now" and it completely express how I feel.