There's no doubt about it, friendships are an important part of life. However, all your other friendships combined aren't as important as the one you have with yourself. Every day of your life you send yourself thousands of messages that determine how you elevate your own worth.
The evaluation you make of your worth is what determines your level of self-esteem. Of course, the messages of love and acceptance we get from our family and friends affect our self-esteem, too. But they don't send even a tiny fraction of the number of messages that we send to ourselves. They don't have the opportunity to affect you.
Besides, if you're continually sending yourself negative, devaluing appraisals, you'll drown out the other messages, even if they're as positive as they could possibly be. It's important that you, yourself, become the source of these positive messages. When this happens, the leverage you'll have from your "inside" position will make enormous change possible in an incredibly short period of time.
Unfortunately, most people spend much more time focusing on their faults and mistakes than they do on their strengths and successes. But it's a skill that can be learned and perfected, and you have a lot of options to help you learn this skill.