Ever wish you could talk to your younger self, the one just beginning his sales career? Knowing what you know now, you could have avoided a ton of mistakes and awkward situations early on if you could just go back in time and give yourself some key pieces of advice.

One well-established sales professional shares his career lessons—the ones he wishes he could have told his younger self. Hindsight is 20/20 after all, and some of the best advice comes from the first-hand past experiences of others.

1. Honesty Is the Best Policy

When you’re young, you’re so focused on getting the sale and meeting your quota in order to impress your boss that it can be tempting to do or say just about anything in order to close the deal. But honesty is the best policy, especially in sales. Tricking prospects to talk to you by pretending to be an old friend, not saying anything when you know for a fact that your product isn’t a good fit for the customer, or being deceptive or dishonest in any other way tends to come back to bite you.

Trust is a critical aspect of the sales process and being dishonest is the easiest way to break the trust and ruin the relationship you’ve worked so hard to build.

2. Research, Research, Research

When you’re young, you’re often overconfident in your selling skills. And this cockiness can lead to a wealth of problems, one of them being that you think you know everything. But you can never know enough about the prospects you’re meeting with and it pays to do research ahead of time. This is the only way to ensure that your presentation will be customized to meet the specific needs of those prospects.

3. It’s OK to Say “I Don’t Know”

It feels embarrassing to have to admit that you don’t know something. After all, prospects are coming to you seeking answers and solutions, and you don’t want to disappoint. But when you don’t know something, you really should just say it. Promising a prospect that you can have a product shipped by his deadline and then realizing later on that it’s impossible will just lead to frustration and lack of trust on the buyer’s side.

Saying “I don’t know” is OK in sales. All you have to do is check on the fact later and get back to the client.

4. Don’t Give Up

Being a sales professional is tough. It can be demoralizing. It can be hard to deal with rejection. It can be depressing to be hung up on all the time or to never have anyone respond to your emails. But these slumps happen to all sales people and it’s the way you deal with them that matters. Pick yourself up, brush yourself off, and continue to be positive and go after those sales. It’ll be worth it. Sulking won’t do you any good.

5. Ask for the Close

I can’t count how many sales I’ve lost as a young sales professional because I was too scared to just ask for the close or because I didn’t want to seem too pushy or aggressive. But the answer will always be no before you ask for it—so what’s the worst that can happen? It can’t hurt to ask. It took me a long time to realize that confidence in asking for the sale really makes a difference, too. When you ask strong closing questions, you get the sale a lot more often than if you use fluffy closing questions because you don’t want to be too aggressive.