there is no doubt it's tough, the things I find toughest are a) having all the responsibility for decisions, no-one to run it through with, get a sense of proportion with, and b) the lack of time to work out my own thoughts, it is relentless, so much so that when I do get a break I literally feel giddy, as if I am not quite tethered to the earth, it's very strange.
Perhaps this is my experience of relationships, but I don't see that having a partner would ease the "downsides".
It would be one more person with needs and foibles to add into the mix, different compromises and accomodations to make: I can't see how that would give me any more time to myself!
My main way of dealing with it is remembering what it was like trying to parent with an active alcoholic in the house (sorry, I know when anyone suggests a gratitude list to me I feel like kicking their smug behind accross the room). I don't have someone to lean on, but no-one is actively trampling me down either, so far all of the diificulties have paled into insignificance besides that experience.
somedays, the only thing I can be proud of at the end of the day is that I have the same number of children at the end as I had at the beginning and I wasn't fired: they may hate me for making them go to bed, they may not have eaten enough vegetables, they may have watched too much TV, the house may be a mess, I may have shouted, and not played enough, there may have been no bedtime stories, I may have been late for work, but nobody died.
and despite their very human mother, they are great kids, who know it's OK not to be perfect.