Learn to love your children unconditionally. Remember that they are individuals who, like you, are developing their own view of the world and want to live in it their way. They don't want strings attached in their relationship with you. They need your love, support and guidance. If you put expectations on them to be or do something in order to gain your love and approval, you may lose their love and respect.
It is hard for many men to tell their spouse or children that they love them. It is not always seen as manly to confess such feelings, and yet that is only reflective of generations of men being afraid to show how they feel. Saying that you love someone is not showing weakness - it's actually the opposite. It says that you are strong enough to put your emotions out there in front of others and not hide them to protect yourself. Telling your children that you love them is the best way for them to build self esteem and learn to be unafraid to show their feelings when they are adults.