While I don't have children, I am single and have had to make the huge decisions on my own so I feel your burden. I realise it probably doesn't really compare to your situation that well. However, it is really difficult and if I personally look back, I know I have used my singleness as a reason not to take the plunge into some new things because I just don't have the support and I am afraid of the plunge alone.
When I need to talk to someone I usually use my brother or my parents as friends aren't close enough for these 'biggies'. And you might think it sounds really naff, but I pray, a lot! Sometimes that helps, sometimes I fully admit it doesn't, sometimes I feel a peace about the decision, sometimes there is nothing one way or the other.

For me, time is the only true teller of if a choice has been the right one - having children would certainly put a whole new spin on it though as it's not just my life I am stuffing up if I do iykwim.

I think the decision making does get easier, as you grow in your own confidence as you make more good choices.