If you agree to something you have get it done. It's your estimation - don't promise what you can't deliver.
Always Be Communicating. In most projects you have to deal with changes and unexpected problems along the way. Talk about it with your client. Be proactive and transparent!
Milestones, Sprints, Deadlines. Every task has a specific date. Do everything to be on time, reduce functionality if neccesary. Uncommented elapsed dates will cast you in a negative light.
Be confident with what you're worth. Avoid incalculable fixed price offers. You will end up paying on top - thats bad for your motivation and the market.
To deliver awesome work you have to push things to the limit. But take care about getting enough leisure time for physical & mental recreation. Having some time outs is most important for creativity & motivation.
You are your own brand. Make yourself visible and find new clients.
IT knowledge expires quickly. Besides blogs, magazines & conferences local meetups are a good alternative to get the latest trends.
Not every new idea, software or framework is the next big thing. A healthy scepticism towards new products is fine. Otherwise you get lost in a jungle of possibilities.
You can get more out of it than you might expect! The new way of work is expanding - besides a desk people find inspiration, help, motivation and friends.
The freedom of self-determination is awesome. You can choose your customers, workplace, projects & wage. That's a privilege - be proud and defend it!