Certainly! If you want to convey a more mature and responsible tone while expressing your support and presence for someone, you can use the following alternatives:
- "You can count on me."
- "I'll stand by your side."
- "I'll be there to support you."
- "Rest assured, I'll be with you."
- "You have my full support."
- "I'm here if you need me."
- "I'll be available whenever you need help."
- "You won't go through this alone; I'm here."
- "Lean on me, I'm here for you."
- "I'm committed to assisting you through this."
These phrases convey a sense of reliability, maturity, and sincerity while expressing your willingness to be there for the person in need.