I didn't know of anyone who breastfed growing up, but was determined to do it. My MIL is an NCT b'feeding counsellor which really helped. I think it can be helpful (at least it was for me) to be aware of the commonest reasons why people stop, and to be either aware of solutions for those problems, or where to go to find help. I honestly think the biggest issue in UK that leads to women stopping is lack of proper support. NHS support is very variable depending on where you live, but NCT breastfeeding support can make up for this.
Having realistic expectations that there may be some issues getting things off the ground, but that most of these are totally solvable, was a huge help to me. DD3 had real latch issues and I was bleeding and in a lot of pain, but I was so glad she was my third as I knew there must be a problem and that it could be solved.
Educate yourself as much as you can, decide in advance how you will seek help if you are struggling (e.g.. HV, midwife, NCT helpline, local breastfeeding group). Also, avoid scheduled feeding like the plague. As an a pp said, frequent feeding on demand is so important to get things going. It's exhausting at first, but does get things going. I set myself small targets, which helped to keep going: feed for six weeks, then get to six months, then get to one year. In the end DD1 fed for 17 months, DD2 for 24 months and DD for 22 months.